The Ubuntu Files app works fine on my new device (Philips Go Connect (Android)) but when I try the Ubuntu One Cloud mode on the Ubuntu Music app it does not manage to sign in but says "Oops something went wrong". This works fine on other devices on which I installed it a few months ago.
I was not able to reproduce your issue. Could you please verify you're running the latest versions of Ubuntu One Files (18.104.22.168) and Ubuntu One Music (1.6.1)? You can verify version number on your device > Menu > Settings > Applications > Manage applications.