I had been troubleshooting for days to figure out why all of my download clients stopped working in Sonarr/Radarr after I upgraded my seedbox to Ubuntu v20. I finally decided to downgrade it again after no one seemed to have an answer for me. All is working again after the downgrade. Has this been documented anywhere?
V20 - so focal?
Sounds like you were doing something very wrong in your setup. Sonarr is compatible with focal
More likely it’s the Ubuntu update. A lot of Ubuntu distros do not like to run the latest versions of software. I ran into that with several distros based on Ubuntu and finally made a switch to Arch based distros and never looked back. I was unimpressed when I had the latest stable version of a program installed and went to do a major update to the OS and was forced to rollback various software to their previous versions all in the name of keeping the distro stable.
It might even be the php version that you currently use.
Activate the debug option on it and check what failures come by.