I had that problem with a Jeep. I tried 3 different mirror kits.
The guy at the NAPA store told me to use clear silicone. I did and it worked.
Clean both surfaces to be mated.
Apply silicone.
tape mirror button in place.
Wait at least 24 hours.
Install rear view mirror.
The rearview mirror on my wife's 2008 Ford Escape fell off last week. I have tried the Permatex adhesive kit they sell, and it lasted about 2 days and fell off again. I followed all the instructions and put it on again, and it lasted around 2 days. A Ford mechanic tells me they see the same problem with Ford's coming into their shop for service. (He said to buy a new windshield - I don't think so!!!) I'm thinking about trying the Loctite adhesive kit they sell for rearview mirrors. Maybe buy a new tab (bracket) that the mirror slides onto and try that? Any suggestions would be appreciated.
The guy at the NAPA store told me to use clear silicone. I did and it worked.
Clean both surfaces to be mated.
Apply silicone.
tape mirror button in place.
Wait at least 24 hours.
Install rear view mirror.