Liftmaster is messed.

When I hit the button the door jerks forward an inch and then stops, the light flashes a few times and then stops. When I disconnect the door the opener operates perfectly and the door moves freely on the tracks. No broken spring or cable and the sensors are aligned correctly.

Do I need to play with the tension settings?

The door/opener are 8 years old and this is the first time I've had a problem.

It sounds like the down force is set too light and needs increased. Increase the force setting but not too much....you still want the opener to reverse if the door closes on something. Check your owners manual for instructions. If you don't have your manual you can find it at Liftmaster.com under Customer Support.

Thank you for the help

Gave it one full turn with no changes.

That's concerning that increasing the down force did nothing. Part of the safety of the operator is being able to control how much force the opener pushes with so not being able to control that could be a serious problem. Possibly a problem with the logic board. But before you go down that road you should remove the cover on the unit (unplug it first) and check the gear assembly. Check the white drive gear and look for any white shavings. It's possible the gear is worn down & not fully engaging.