I just experienced the same thing, but unfortunately I am probably not going to be a great deal of help. I had to replace my phone, and when I tried UD Mobile, I had the same issue as you, same message about firmware even though nothing had changed. No problems with Admin Console, etc.
The problem is, I screwed around in the UD Mobile app and somehow got it to work. I failed Troubleshooting 101 (Remember your steps.) I'm back up and running with UD Mobile, and don't know how to get it back to that error screen. I'm not exactly sure, but I think I may have pressed + to add another controller. I had to enter the local username and pw, and the next thing I knew, it was loading everything. Everything is back to the way it is, and I'm still on 5.0.16.
I'm sorry I can't give you any instructions that are better than "just keep trying stuff."
yessir