Howdy Friend!
Always nice to see Android developers start using JME.
This is an issue that has to do with the application not closing correctly OR attempting to restart the mainactivity after one is already running (why this is the case I don’t know).
Usually the key is opening in portrait mode when you want landscape and JME by default doesn’t handle this.
The key is you must kill your application process properly on closing the main activity.
This post should help you through it as it is a common problem on JME and is explained there.
Good luck!
<3’s
BigBawb