502 Bad gateway illustrates that while performing as a proxy or gateway, the server received a non-valid response from the upstream server it accessed in the attempt to fulfill the request being made. this error usually was caused by bad IP address conversation
between background servers, you can try clear your browser cache completely and closing your browser or rebooting your computer and verifying your router firewall is not having issues before assuming it is the website itself. also you can ask the website administrator
to fix the problem. For more about this issue, please check the following articles.