I wanted to state that I found both a problem (that I stated yesterday) and a solution as well. So here it is:
Problem: Mobile beta 1.5.6 gives Notifications Broken error on the start
Solution: On the wiki page, follow the instructions said to uninstall and re-install the app, and that should be fixed ^^
and if that didn't work....
Problem: I was logged in already and doing fine before, and suddenly the notifications broke again (and the available pawn doesn't work)...
Statement from experience: I've been though this a few times now, so if you login from your computer and go back to mobile, this happens.
Solution: First thing you want to do is restart your phone. When it turns back on, uninstall the app, and then re-install it again. Then enter your login credentials, check your email, etc. When you do that, and you're in successfully, it should show the Notifications broken popup one more time, so repeat the uninstall, and reinstall, and login. After this, the problem should be solved and the Notifications should not be broken (and availability pawn comes back too)
I had this from experience and tested this a few times myself, so I thought it would be helpful to others who are experiencing the same problem to follow these steps also. I hope this helps ^^
Edit: I also want to slip this in here, the disclaimer that states this may not work on all phones. When I get the chance, I will test this also on my second phone