Some older P3 boards require you to press the remote button twice in quick succession during programming. If the single press fails, try pressing the remote button 3 times rapidly (a "tri-tap").
Technical Documentation Assistant Date: Current For official use only – Always refer to the original LiftMaster manual for your specific opener model. liftmaster garage door opener p3 security 2.0 manual
Since you don't have the physical manual, you will rely on the diagnostic LEDs on the P3 logic board. After a failed operation, count the number of flashes (or the Learn LED flashes) on the motor unit. Some older P3 boards require you to press