In some rare cases Push mode is not functional (the "Push Notifications are disabled. Pull service will be used." message is shown on startup and an appropriate option is not allowed in the Settings). The following are steps to fix it:

1. Install latest mPD version (v2.2.0) from AppStore. 
2. Run app first time and ensure that Push is broken. 
3. Remove app from background. 
4. Go to the iPhone's "Settings | mPD" and turn the "Fix Push" option ON. 
5. Start mPD and ensure that Push is functional . 
6. Go to the "Settings | mPD" and turn the "Fix Push" option OFF.
7. Use app as usual.