When the product lifts at the free edge, which is the tip of the nail, it is often because the free edge has not been sealed thoroughly with base coat, color coat, and top coat.
It may also be because the seal has worn away over time. This can happen, for example, if you have filed your nails after application, use a computer frequently for work, or often have your hands in water, such as when cleaning.
Gel polish is not a flexible product, which means that if your natural nail bends underneath it, the gel polish may start to lift from the tip of the nail. The product can also lift if the nail has been knocked or bumped, as this can damage the gel polish and cause it to loosen.