The mount for the Cycleaware Reflex mirror (and pretty much all the other brands) relies on double sided sticky tape. I have never found a sticky tape that is actually long term reliable on any surface and in any weather - sooner or later, either the tape fails or the surface it's stuck to releases.

This is a replacement, you can either print it plain or add your choice of bases. I have attached one with a 30 degree angle set of zip tie holes underneath, but you can attach the basic base module to anything you like.