I’ve found a couple of reasons why glued nails come off. The first is that, because they are usually curved more than your nail bed, you don’t use enough glue to fill the gap fully. Add plenty of glue over the whole nail surface, and press the nail down hard until it’s fully set. The other reason is that the join usually fails between the glue and the false nail, not between the glue and your nail. If you roughen the back of the false nail with a bit of sandpaper before applying it, this will prevent the joint from failing. Last month I was wearing a set for 3 weeks and I only had one failure. It was a bit of a bugger to get them off (they had grown out) so nail wraps are on my next shopping list.