The reason it doesn't hold when you glue it could be because of the profile of the surface inside the broken area, so maybe it can't bond correctly.
You'll have much more chances of making this work if you use dedicated rearview mirror adhesive kits (Loctite and Permatex make them), or maybe 3M VHB tabe (the one used for camera mounts and such). A dashcam camera mount glued to the windshield usually breaks the windshield if you try to force it out - you have to use cutting wire to get it off safely.
In all cases, if your epoxy spread all over the place you might have to clean it first.
Can't hurt to give a call to 3M too, they should be able to point you to the correct product.
You'll have much more chances of making this work if you use dedicated rearview mirror adhesive kits (Loctite and Permatex make them), or maybe 3M VHB tabe (the one used for camera mounts and such). A dashcam camera mount glued to the windshield usually breaks the windshield if you try to force it out - you have to use cutting wire to get it off safely.
In all cases, if your epoxy spread all over the place you might have to clean it first.
Can't hurt to give a call to 3M too, they should be able to point you to the correct product.
