LiftMaster opener will not run; both UP and DOWN arrow LEDs flash alternately or together.

Safety: If you are not comfortable working with household electrical circuits, contact a licensed electrician.

• Check outlet: Plug a lamp or known-good device into the opener's outlet to verify proper voltage and stability.
• Try another circuit: Temporarily plug the opener into a different outlet on a separate circuit using a heavy-duty extension cord to see if the issue clears.
• Inspect wiring: Ensure the opener's power cord is not damaged or pinched.
• Check for shared loads: Avoid running the opener on a circuit heavily loaded with other appliances.
• Logic board power supply: If line voltage is good but the LEDs still indicate a power fault, the internal power supply on the logic board may be failing and the board should be replaced.