Within the last couple of days, the rocketchat app on my server has stopped working. It has been working just fine for months. And then something changed recently. When trying to access the https://server/rocketchat, the reported error is:
The proxy server received an invalid response from an upstream server.
The proxy server could not handle the request
Reason: Error reading from remote server
Apache/2.4.25 (Univention) Server at tars-mail.tarstrucking.com Port 443
The host server is: UCS 4.4-4 errata 579
Rocketchat app is: 3.0.2
The server also has kopano, kopano webapp, nextcloud and guacamole apps all running just fine.
I tried uninstalling and reinstalling the rocketchat app. I still get the same error.