A couple of years back i replaced the broken aerial with a aerpro one on my TJ Magna.

Yesterday when cleaning the car i knocked the rubber washer/gromet that sits between the aerial and the panel of the car.

It's now just hanging there with 90% not underneath where it should be. I can't slide it back under. Can you unscrew the aerial from the top and slide it and then screw it back under? Buy a new rubber washer etc??

Thanks.

You should (hopefully) still have the little tool that unscrews the nut at the top that you got when you bought the replacement. Take it off and fix the seal. If you don't have the tool, use a smal screwdriver to prod it back into place.