Issue 502 Bad Gateway nginx - have not changed anything

[Another_Omeka_User]

Server operating system version

CentOS Linux 7.1.1503 (Core)

Plesk version and microupdate number

Plesk Obsidian Version 18.0.58 Update #2

Getting a 502 Bad Gateway on the domain we've hosted for a while now. Not really sure what happened as we haven't changed any of the settings on it in years... the only nginx setting I have running (under Hosts/DNS) is a redirect. Have not changed anything. I checked the nginx access logs, but they're gibberish to me. Not really sure what my next steps should be. Is there a troubleshooting guide on where to go from here......?

 

[Another_Omeka_User]

To be clear: I mean our domain/website under "Subscriptions."

 

[Another_Omeka_User]

Update: Restarted the server and now I'm getting a "ChunkLoadError" when I click on "Subscriptions". I refreshed the page and can now see the domain... does anyone know if these issues would be caused by outdated php? I run an older version of php on this particular domain because it runs an older (outdated) webapp for something quite specific.