I have a server from the guys at time4vps.eu where I am running - among other things - an ownCloud instance. It was basically just a learning exercise to get it up and running, maybe invite a few friends if interested. Then I started also looking at certificates from letsencrypt.org and set up some sub-domains for my server.
The point where I ran into an issue was after I set up my sub-domains and the required encryption certificates. For some reason the browser login would work, but on my Android device I got an error from various apps saying,
"Server not Installed!"
This was weird, because desktop clients were syncing with absolutely no problem.
I was clueless for a long time and honestly demotivated to fix this, because I wasn't using it so often. Nevertheless, it was bothering me and whenever I logged into my server I remembered that something is broken and needed to be fixed.
I have spent hours trying to troubleshoot, unfortunately the error logs
were empty or contained nothing related to the issue.
Finally after some IRC help and searching I stumbled upon the solution at forums.owncloud.org,
In /var/www/owncloud/config/config.php I had an entry
'installed' => 'true',
this had to be replaced by
'installed' => '1',
I have no clue as to why or how this error occurs, however possible there are some issues with the installation. Nevertheless, after changing this entry and restarting my apache the Android client worked right away.
Note: Depending on your installation of owncloud config.php might be elsewhere, e.g. /var/www/config/config.php if you installed it to the "root" web directory.
Editing the file is done by sudo nano /path/to/owncloud/config/config.php
I am troubleshooting further to find the true source of the error, but one issue has been fended off.