Using the IOS app, I have seen the same thing when I last reset my A+ after adding an unsupported sensor. Suddenly, I could not see any sensors on the IOS app. In order to recover, I tried the following:
1. Rebooted the A+ (no help)
2. Followed the procedure to remove "ghost" sensors (no help)
3. Ran diagnostics (no help).
4. Removed one of the sensors that was working, re-added it.
a. At this point, all my sensors showed up on the app but were unresponsive, with none of the usual controls.
b. I toggled the sensors from the A+ and they fixed themselves as I toggled each one. For the motion sensors, I triggered it and it was fixed.
After I "recovered", I have added more sensors and switches without issue. I have also rebooted without issue. I have no idea what happened, but it was weird.