We are receiving BadGateway (502) response from your proxy server ({0}). This typically indicates either your proxy server ...

We are receiving BadGateway (502) response from your proxy server ({0}). This typically indicates either your proxy server support doesn't support {1} traffic or there is some network connectivity issue going on the path from proxy server to Office 365 servers that your proxy is trying to connected to. You may want to bypass proxy to check if the issue is still persists.