Here are some ways to reattach a zipper:

1. Use a pair of pliers or a fork to remove the stopper at the bottom and reinsert the teeth into the pull.
2. Use a sewing machine or glue to reattach the zipper, depending on the damage to the zipper.
3. Replace the zipper pull to fix the problem.
4. Gently move the zipper up and down on the track to get it readjusted.
5. Try a spritz of WD-40 to oil it up.
6. Use a pin or needle and stick it into the zipper or along the track to get it to move or force it back together.

If you want more detailed instructions, you can check out this [step-by-step tutorial](https://silverbobbin.com/how-to-put-a-zipper-back-on/) from Silver Bobbin.

I hope that helps!