The product still being on the nail is a good thing, that helps us eliminate it being a curing problem.
This could be from a few different things though…
Gelish® Soft Gel Tip Primer – ideally you want to re dip into the bottle every 1 or 2 nails to make sure you have enough primer on the brush to add to the tips. This is what is going to give you the bond between the Gelish® Soft Gel Tip Adhesive and the Gelish® Soft Gel Tip, and not enough Gelish® Soft Gel Tip Primer could mean less of a bond. Gelish® Soft Gel Tip Primer should be applied to only five tips at a time so the product does not dry prior to applying the tip.
Applying too much pressure and making the tip touch the natural nail – if you are pressing to hard when applying the tip for the flash cure. Keep it as a medium pressure when applying. This could also be from not using enough adhesive – meaning you have to press more to get it to spread. Remember there is supposed to be a gap between the natural nail and the Gelish® Soft Gel Tip that will be filled with Gelish® Soft Gel Tip Adhesive. Also, make sure to use enough Gelish® Soft Gel Tip Adhesive.
Tip too small – if your tip is slightly too small you will need to apply more pressure to get it to fit, resulting in not enough Gelish® Soft Gel Tip Adhesive between the tip and the natural nail, which can result in it ‘popping off’.
Finally double check what your client is doing, it could be something as simple as the nail was banged or put under pressure and the nail came off rather than causing damage.