The new aircraft (Mavic/P4P/I2) all required user input to finally land. Just hit down on the throttle just like you would if you were manually landing. All you have to do is tap it and it will land.
If you want to land yourself, switch out of P mode and back into it and manually land. If you don't switch it back into P mode Map Pilot will miss events from the aircraft and get out of sync.