Exactly the same problem.

A/c no longer follows flight plan. Autopilot  buttons are all clickable but have no effect on the aircraft.

Addons:
AS P3dv5
Rex Sky Force

Hi Dario

I think I've found the answer.

Our problem seems to be caused by Rex Sky Force and how it affects Simconnect during a long flight ( after aprox 7 Hours ). I came across a lengthy thread on the P3Dv5 forums which had the solution of not connecting Rex Sky Force when doing a long flight.
I have just flown EBBR to KMIA in the CS767 and the flight went perfectly. Previously I had tried to complete the flight numerous times trying various things including disabling scenery, reinstalling etc but with no success.

Don't want to speak too soon but I think this has done the trick. Obviously if this is correct then Rex need to sort the problem.

Cheers