Have you tried contacting Nemo? That might be a good starting point.
Since you’ve had it for years, you want to be careful about following advice or using products made for current tents. Materials, coatings, and construction methods used on your tent may be significantly different from those used today, and might not respond well to current products. The original manufacturer might be able to help you sort through all of that.
Loc: Torrance, CA
PU coatings wear out over time. If its a bit sticky, smells a bit funky, and isn't very waterproof there isn't much you can do for it. They sell coatings you can reapply, but you have to remove the old stuff first. People who have done that report it was a ton of effort and didn't work all that well.
I wonder if the old stuff would clean off easily with "Goof Off"? Be sure to try it on an unimportant part first. Here from something I found on line and cut and pasted; Celina Citrus Cleaner is a 100% biodegradable solvent that quickly removes adhesive residue from tents, inflatable bouncers, PVC, and plastics. This cleaner completely removes tough substances like engine grease, tar, paints, inks, adhesives, shoe polish, crayon, kitchen grease, and more. A diluted solution of 1:5 bleach to water can be used when general maintenance cleaning for more stubborn soils, but will not remove stains. Isopropyl alcohol or mineral spirits are also helpful in removing gummy residue or wet paint. Be sure to remove any excess cleaning solutions with a clean, dry cloth.