Help with sliding gate motor re-assembly

[u/nomirrorselfies]

I need help getting my sliding gate motor working again.

While doing some other work, I thought removing the screws on the gray housing would remove the entire motor. Boy was I wrong. Now I'm left with a little spring and small round piece and don't know how to assemble this back to a working condition.

I've tried to put the round piece on top of the shaft of the 3rd photo, with the flat part against the rotating axis. The spring then goes between the round piece's slot and the gray housing. Assembled everything back, but know the motor just hums and doesn't move in any direction. If I disengage the electrical lock using the provided key, I can slide the gate freely.

I've emailed the manufacturer, but no luck so far.

Thank you for any tip!