It's been on window for 20 years. I've tried everything.
Try 90 percent alcohol. . Also a razor blade . Worth trying. .Good luck. .
Have you tried hearing it with a hair dryer and peeling it off?
I have heard that straight ammonia sprayed from a bottle then cover with plastic wrap and after about 45 minutes remove with putty knife.
Hi Mary, Try to peel a corner off a little, and squirt vinegar down on it. If that don't work try goo-gone, follow the instructions on the back