Unfortunately I had to experience the same thing with my m8 and the Mercedes sap v3 cradle. The m8 runs android 5.01 newest 4.16.401.10 firmware. Tried native rsap and your app multiple times. The phones shows successful pairing, while the car doesn't. I happen to been able to connect my new one m9 (android 5.02) with native rsap like a charm. It's really bothering me, because my dad needs his m8 connected to the cars Bluetooth system. One M7 on android 4.44 worked perfectly with your app before as well. The M8 is rooted. I hope I can help to find a solution somehow.