Garage door worm and drive gear were replaced. Evrything appears to be replaced properly, but even without the chain on, the door moves only a few feet then reverses.I checked to be sure the motor shaft was pushed out as far as possible before tightening the collar.

yes, and not that bad of a job. parts on eBay or other online sites.

If it is not blinking when it stops, then the capacitor is blown. Replace the capacitor and it should resolve the problem.

I had to retension my spring assembly on the garage door a few years ago and I don't recommend anyone without proper tools and some experience to do it. It can be dangerous.

Fool with the down and up force adjustments on the back of the opener.

If your garage door has the sensors at the base with a laser light, check the aim of them.

Binding on the track?

Check to see if the 4 wire harness is hooked up from the limit assy.

When mine did this, it was because the nylon gears that drive the chain had stripped. My wife had to live without the opener for a week or more, but I was able to find a new gear kit online and replace the damaged gears. It wasn't difficult.
The other option is to buy a new opener.

I have the same problem. I just removed the cover and discovered a nylon gear had been worn out. I found lots of shavings inside the cover. The nylon gear is beneath the exterior chain gear. I am looking for information on how to replace it, if I can find the part. If you decide to look at yours, unplug the power and remove the sheet metal screws securing the bottom portion of the cener cover to the front and back covers. Then just remove the upper screws from the center cover. Good luck.