I suspect its got something to do with the systemd service definition. You may have to tweak the parameters under “optional security settings” to make it work. Or maybe you could start radicale manually from the command line, just for testing, and see if that works
I don’t know if you’re using debian but I encountered the same issue. The wiki has instructions to fix this (section create essential directories):
I hate this message
I’ve just set up Wireguard, so I can access my home network from everywhere, but the old laptop that I wanted to use as a server has just quit. So now I have to find a different machine
Can you maybe give us a ls -Al of /var/lib/radicale and /var/lib/radicale/collections to double check the permissions? I just looked at the systemd documentation and the service definition looks ok.