Before reinstalling the mirror holder to the inner holder (A) of the actuator, check the actuator rods (B) and the actuator boots (C):
If each rod is off the actuator hole, insert it securely.
The whole of each rod should be covered with the boot. If not, adjust the boot into proper position.
Reattach the hooks of the mirror holder to the actuator, then position the mirror holder on the actuator. Carefully push on the clip portions of the mirror holder until the mirror holder locks into place.