I have my own 9.0.4 installation, and it has been working perfectly on OSX 10 and various Androids, but today I installed the client in my IOS 10 iPhone, and I only got "server not found". After some troubleshooting I found that the IOS client was requesting '/status.php' from the webserver, and not /owncloud/status.php as it should have done. I linked the owncloud status.php into the location from client app request, and now it connected fine. I had to do the same with remote.php to Get authentication to work. From then on the Owncloud IOS client worked perfectly.
I guess it should be addressed from within the client, but how?