While it is disengaged check to see how smoothly the door closes manually. See if he has greased the tracks of the door. This shouldn't be done but some people do it. If he did clean the grease up. If everything checks out okay you will find a control on the rear of the motor unit near where all those white wires go labeled "down/close force". Adjust this just enough to get the door to close. It affects the safety system so don't over do it.

I agree with Don. I just had a gdo replaced and the guy told me sometimes in winter the door needs just a little more uumph to open so you should adjust the force. He said that will definitely fix it.