'72 Mirror won't stick

[mister.freeze]

So, for the last 2 years, I haven't been able to keep my mirror glued to the windshield very long. The previous 20 years, I think I had to glue it on maybe twice. I've used several of the different glue kits like Permatex, but those lasted 2 months at best. It was a hassle, so I just kept some super glue in the truck which did no better. Ran out of that and tried Gorilla glue. about the same.

Yes, I clean the button AND the glass before hand. Yes, I use tape to hold it in place. I've done it at night and in the middle of the day. It will fall off during the day while at work, while driving, and even overnight. What gives?

It's like that part of the windshield has just quit letting anything stick to it for very long. Thoughts?