Oil the chain
There should be two adjustments on the motor control, an UP tension and a DOWN tension. increase the DOWN tension a quarter turn after you've oiled the chain. If it gets farther down but still stops, add more tension in quarter turn adjustments, until it closes.
The sensor works in conjunction with the tension if the tension is too low, no matter how perfect the sensors are aligned, the door will find a reason to stop.
Is it just stopping? Or is it stopping and then opening back up. (Yeah, been down this road.)
If the sensor senses a "blocking of the stream" of light. It stops and goes back up. Whether that's real, or a faulty sensor depends on how many pets or how much crap you have in front of the door.
If the system senses a blockage above the sensor lens, it stops the door closing (or opening) process. This is where tension comes in. Too much tension, it stops. Cold metal doesn't like to move. Every winter, I have to adjust this, with the tension screw settings. Adjust slowly, test in quarter turns, as described above.
Also might want to remove the cover and look for plastic shavings in the casing. Those fiber plastic gears are (IMHO) designed to wear out. Make sure the power is off to the unit. I do not recommend repairs to the unit. (I've done it once, and then got to do it again.) Replace the silly thing.
At what point "Do it Yourself" stops and common sense takes over, is kind of up to you and your free time.
ETA: Almost forgot. This does not preclude the kicking Rob step.