Opener motor runs but the door does not move; chain or belt moves but trolley stays in place.

Safety first: Ensure the door is fully closed or securely supported before re-engaging the opener.

• Re-engage trolley: Pull the emergency release handle toward the opener head until it clicks back into the engaged position. On some Mighty Mule models, running the opener in the close direction will automatically re-engage.
• Check door arm connection: Verify the curved door arm is securely bolted to the trolley and to the door bracket.
• Inspect trolley: Examine the trolley carriage for cracks or missing teeth where it engages the chain/belt. Replace the trolley if damaged.
• Test operation: Run the opener and confirm the trolley now moves with the chain/belt and the door travels normally.