The arm has two racks - one at the top and one at the bottom. When air is re-applied, it seems your bottom rack is pushing the arm out of alignment before the vertical cyulinder starts to lift it.
Pull the arm into alignment and lift it slightly (about 1/2") and put a piece of wood under it to keep it from engaging in the bottom rack. Keep the middle right solenoid button pressed, apply the air and allow the arm to rise. It should put the racks in the right place to carry on.
If you can lift the toolchanger arm in any position, it'll need to come off to have the little key replacing at the bottom of the assembly.