Troubleshooting Common Proxy Errors
A proxy server can stop working for many reasons – from authentication error to connection issues and misconfiguration. As a result, you lose access to websites, APIs, or other resources. Even experienced network users sometimes face a proxy error with a message that doesn’t explain the root cause. In this guide, we break down the main failure scenarios, their types, and how to restore a stable connection.
What is a Proxy Error: Causes and Core Types
Such an error appears when the intermediary can’t process a request or establish a connection to the target.
Broadly, there are four categories:
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Connection – no response or the connection drops (408, 502, 504).
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Authentication – invalid access credentials (401, 407).
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Access – restrictions by IP, rate limits, or insufficient permissions (403, 429).
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Configuration – bad client or server settings, DNS issues (400, 404, 500, 503).
Each category requires a different diagnostic and remediation path – that’s what the next sections cover.
How to Fix Proxy Error: Common Issues and Solutions
To pinpoint why your proxy server is not working, you need to know what each specific status code means and what to do in that situation.
400 Bad Request
If the page won’t load even though the connection is established, the intermediary is likely receiving a malformed request – corrupted headers, an incorrect URL, extra spaces, or stale cookies. Your browser or antivirus may also be rewriting the request.
Clear the browser’s stored data (cache and cookies), disable extra extensions, and make sure the site address is entered correctly. Also verify the protocol you’re using – it must match what the target host supports (HTTP/S or SOCKS5). If the proxy error persists, reset network settings.
401 Unauthorized / 407 Authentication Required
An authorization prompt means access is restricted either by the website/API (401) or by the intermediary server itself (407). In both cases, the cause is the same: credentials aren’t being sent, are wrong, or an access token has expired.
Re‑enter your credentials in the browser, OS, or application settings; verify the Authorization and Proxy-Authorization headers – there must be no stray characters. You can inspect this in the browser’s developer tools: open the Network tab, select the request, and check the headers.
You can also verify with a special tool such as cURL. Open a terminal and run:
curl -v -H "Authorization: Bearer YOUR_TOKEN" https://example.comIf you use an intermediary:
curl -v -x http://username:password@ip:port https://example.comAfter execution, check the Authorization and Proxy-Authorization lines in the output — they show exactly what is being sent.
If you authenticate with a token, generate a new key in your provider’s dashboard. For manual configs, ensure the format is username:password@ip:port.
403 Forbidden
If the connection is established but you see a proxy error with code 403, the origin rejects the request. Possible reasons: your IP is blocklisted, the site gates traffic by region, you exceeded call limits, or you picked the wrong protocol.
Switch to an intermediary in another region. Check whether you’ve hit rate limits and confirm the protocol setting is correct. For recurring restrictions, use IP rotation or private solutions, which provide more predictable throughput than shared endpoints.
404 Not Found
Sometimes the connection succeeds but the page still won’t open – you see “Resource not found.” Such an error in this context often points to how the intermediary handled the request: it may have truncated the path, added extra characters, or mis-encoded the URL.
To fix this class of proxy server issues, make sure the URL is passed through unchanged. Try opening the resource directly, disable unnecessary extensions, and verify the request string isn’t modified in your browser or script before it’s sent.
408 Request Timeout
If a page hangs and then shows a timeout issue message, the client waits too long. Causes include a weak connection, an overloaded node, or an overly aggressive client timeout.
Increase the timeout (if configurable), reduce concurrent requests, and check network stability. Switching the port or using an IP with lower latency and faster response times can also help.
429 Too Many Requests
A 429 response means calls from your IP are temporarily limited. This is common during scraping, bot activity, or heavy data downloads.
Reduce call frequency, add delays between calls, or use IP rotation to spread load across multiple addresses. For data collection, prefer official APIs and follow the site’s robots.txt directives – this ensures compliant interaction and respects published technical limits.
500 Internal Server Error
If you see 500, your request reached the server but wasn’t handled successfully. Typical causes include software faults, misconfiguration, node overload, or routing issues.
Refresh the page to rule out a transient glitch. If it repeats, check whether the site loads directly. If it does, the problem is likely on the intermediary side – it may be overloaded or misbehaving. Switch to another endpoint or reduce parallelism to decrease load.
502 Bad Gateway
A 502 indicates that the new IP connected but didn’t receive a valid response from the upstream server. Usually the page stalls during loading and then shows a gateway error.
Check if the website is reachable directly, confirm the host and port are correct, and restart the connection. If you chain multiple IPs, test each hop independently to see where the response is lost. For diagnostics, you can use a dedicated proxy checker.
503 Service Unavailable
“Service temporarily unavailable” means the proxy (or the site) is overloaded and can’t process the call. This happens during peak load, maintenance windows, or network incidents.
Try again in a few minutes. To avoid stale cache effects, flush DNS — on Windows, open Command Prompt and run:
ipconfig /flushdnsIf the error persists, switch to another IP or lower your call rate.
504 Gateway Timeout
Here the page loads for a long time and then shows “Gateway Timeout”, or the network drops. Most often, the origin is overloaded or there are delays along the route. Sometimes the intermediary itself is at fault – especially when the request traverses multiple nodes.
To fix problems with proxy servers of this type, first check if the site opens directly. If it does, increase the client/server timeout. If disconnects repeat, trace the request path and, if needed, switch to a more stable node with lower latency.
Connection Refused
This proxy error means the connection never establishes — the browser or app immediately reports it was refused. Common causes: wrong IP or port, the service isn’t running, or a firewall is blocking the session. In some cases, the protocol is incompatible (for example, HTTPS vs. SOCKS5).
Make sure the host is up and the port is open. You can check from the command line.
On Windows (cmd):
telnet IP PORTOn macOS or Linux (terminal):
curl -x IP:PORT https://example.com -IIf the port doesn’t respond, choose another one or restart the intermediary. If the connection succeeds but the issue remains, verify your antivirus or firewall isn’t blocking traffic, and that you’re using the correct protocol and credentials.
DNS Lookup Failed
If the browser shows “Waiting for response” for a long time and then “Server not found,” DNS resolution is likely failing. The address remains in the bar without a lock icon, and reloads don’t help.
This means the domain name couldn’t be resolved to an IP address. Common reasons are a busy or unreachable DNS resolver, or selective blocking by that resolver.
Switch to a different DNS service – for example, Google DNS (8.8.8.8 and 8.8.4.4) or Cloudflare (1.1.1.1) – then clear the DNS cache.
On Windows (console):
ipconfig /flushdnsOn macOS or Linux (terminal):
sudo dscacheutil -flushcache && sudo killall -HUP mDNSResponderIf the problem persists, try specifying the site’s IP address directly instead of the domain name. That helps confirm whether DNS is the root cause rather than another network constraint.
See also: “DNS – what it is and why it matters”.
SSL Handshake Error
If the page won’t load and the browser shows a security warning, a TLS handshake fails. You might see a crossed‑out lock with a “Details” or “Go back” prompt.
Typical causes: expired or invalid certificates, incompatible TLS versions (for example, 1.0 vs 1.3), cipher suite mismatches, or interference from antivirus software. Sometimes the intermediary intercepts HTTPS but doesn’t support the required security parameters.
Open the site directly to confirm availability. Clear cache and temporary files. Check the device’s date and time zone: incorrect settings can make valid certificates appear invalid. If you use an antivirus, temporarily disable HTTPS inspection and test again – it can block establishing a secure session.
Conclusion
Most failures stem from unstable data paths between the client and the origin. Common culprits include incorrect settings, overloaded nodes, or transient network issues. One‑off errors often point to DNS, authentication, or routing. If problems repeat, reassess the connection method you’re using.
Free endpoints tend to be less stable and more constrained, while paid options typically provide consistent connectivity, faster response, and fewer disruptions. For stable scraping, automation, or corporate integrations, consider to buy proxy from a reliable provider – private services help maintain predictable performance.
FAQ
Why does a proxy error appear in one browser but not another?
Some browsers use their own network stack and cache. Issues are often caused by an extension, plugin, or saved cookies. Reset the affected browser’s settings or launch it in safe mode.
Can antivirus software affect proxy operation?
Yes. Some antivirus products intercept HTTPS traffic and interfere with new connections. If issues started after installing security software, temporarily disable HTTPS filtering and re‑test.
What if proxy errors happen only on a single site?
In that case, the root cause is probably on the site’s side. It may block certain IP ranges or traffic types. Change the region or service type and try again.
