Claude Error Codes: Login Failure & API Timeout Fixes – Troubleshooting Guide

When using Claude, login failures and API timeouts can slow down your workflow. This article covers the most frequent Claude error codes and offers a clear troubleshooting path to help you resume normal use.

Login Authentication Error: "Invalid credentials"

If you see "Invalid credentials" or "Authentication failed" when logging into Claude, it means your email, password, or API key is invalid. Start by double-checking your email and password — watch for case sensitivity. For API users, verify that your API key hasn't expired or been revoked. Generate a new key from the Anthropic Console and update it in your setup.

Another common cause is browser cache conflicts. Clear your cookies and cache, then try again. If the issue persists, switch networks (e.g., from Wi-Fi to mobile hotspot) to rule out a temporary IP block.

API Request Timeout: "Request timeout"

When calling the Claude API produces "Request timeout" or "504 Gateway Timeout," it usually points to network latency or server overload. First, check your local internet speed and use ping or traceroute to test connectivity to Anthropic's servers. If latency is high, try a more stable DNS (like 1.1.1.1) or use a proxy to speed things up.

Also, adjust the timeout parameter in your API requests to at least 30 seconds. If batch requests trigger frequent timeouts, reduce concurrency and implement exponential backoff retry logic to avoid overwhelming rate limits.

Rate Limit Error: "Rate limit exceeded"

Sending too many rapid requests triggers "429 Too Many Requests" or "Rate limit exceeded." This is a normal protection mechanism. The fix is to reduce your request frequency. Check the API response headers for X-RateLimit-* fields to see remaining quota and reset time. Implement request queuing in your code with at least a one-second gap between calls. Paid users can upgrade their plan for a higher rate limit or apply for a quota increase.

Note: Many users mistake 429 for a permanent ban — just wait a few minutes and retry. It usually resolves on its own.

Permission Denied Error: "Forbidden" or "Permission denied"

Getting a "403 Forbidden" when accessing certain Claude features means your account lacks the right permissions. First, confirm your subscription tier supports the feature — for example, Claude Pro users get higher concurrency. If using the API, check that your API key's scope includes the required resources. For team accounts, ask your admin to verify your role's access level. Some regions may be blocked; try switching your VPN to a supported location like the United States or United Kingdom.

Another possibility is using an outdated or incorrect endpoint URL — for instance, writing /v1/complete instead of /v1/completions. Double-check the official documentation for the exact endpoint path.

Unstable Network Connection: "Connection refused"

"Connection refused" or "ECONNREFUSED" typically means your device can't reach the Claude servers. Start by checking if Claude is under maintenance — visit the Anthropic Status page. If a local firewall is blocking outbound ports, make sure ports 443 and 80 are open. Corporate networks often restrict AI services; use a personal hotspot or ask your IT department to whitelist the domain. If you're using a self-hosted proxy, confirm it supports WebSocket — Claude's streaming responses require WebSocket protocol.

If nothing else works, restart your router or try a different ISP. Sometimes ISPs perform DNS pollution on API domains — manually setting a custom DNS (like 1.1.1.1) can resolve the issue.