We have a Nextcloud Hub 21.0.2 instance served by Caddy behind HAProxy performing reverse proxy and SSL termination.
All has been well, this has worked with ownCloud and Nextcloud and has served us well for many years. Unfortunately, and silently, the Android app on multiple phones and devices lost connection. Browsers on the same devices work on and off Wifi as well as on other platforms. I wish I could say what changed, I just can’t say WHEN it broke; I am assuming earlier this month it was working fine.
I’ve seen many forum hits on the subject, but nothing that I have found to offer up much hope.
Needless to say, I have many other web applications served by this same/similar implementation and this is the only one that is giving me fits and I have nothing meaningful in the logs on my server(s) that are helpful.