I have had this problem before and I did a few things and got it to close. I noticed my chain looked a little loose so I tightened it.
There are also an open force and down force screw on the opener that may need to be adjusted. The opener has force tension sensors that will reverse the door if it closes on an object. These can get out of adjustment over time and may need adjusted for your door to open and close properly. I know they are used so you don't close the door on something and damage it. When the door comes down on an object it should sense that its tension has changed and reverse the door and go back up. So if these setting are off the door won't go down unless you pull it down by hand.
After I tightened the chains slack and messed with the open and down force screws The door has worked great since.
Hope this helps.