If you received an error while making a request, visit Dedicated Datacenter Proxies documentation. Here you will find a dedicated section - Response codes - with all the error codes explained. You can also find them listed below.
407
Proxy Authentication Required - You are accessing proxy through 60000 port, but you have not provided authorization header, or your credentials are incorrect.
504
Gateway Timeout - Proxy server timed out. Waiting for a response from the target server. Usually about 60s.
503
Service Unavailable - Failed to connect to the target server. DNS failure to resolve the target server address.
401
Unauthorized - Incorrect credentials.
404
Not Found - The resource specified could not be found.
500
Internal Server Error - We had a problem with our server. Try again later.