I have exactly the same problem with the Fenix not moving despite chocs etc having been removed - this only happens in the fs2024 - however at one stage I thought it was related to the plane being parked at a gate but its not as simple as that; placing the fenix on a remore ramp has often worked for me, but not at EGLL .
One hint for the developers might be the fact that when I 'park' on a runway and remove the brakes the plane does move .Such a shame.