Sunroof tracks are tricky. You could have a broken guide.

Can you manually retract the sunroof? If so, do it halfway, pop the sunroof headliner where there are tabs in the front of the assembly, slide the headliner out and you should have access to the sunroof mechanism from underneath.
I find it easier at this stage to close the sunroof then remove the bolts that hold the actual sunroof sheet metal to the supports. Once out, I can stand up on the car seat and easily work on the mechanism from any angle. I also take the cable bolts out so that way I can slide the sunroof frame/support in and out by hand right where I am. This allows full access to the side guides and tracks.
If you need to remove a guide from either side, you will need to unscrew the screws holding the track down from the top.
It's actually easier than you think as long as you NEVER force anything EVER. Don't ask me how I learned that...