Bubbles under a tip application can be caused by using the wrong type of adhesive for that nail shape. If your client has bitten, ski-jump, or ridged nails, a thin adhesive will not full in these imperfections, and bubbles can form in the gaps. Use a thicker adhesive product on these clients. Tips that pop off easily have not been properly fitted. To fit a nail, look down the barrel of the nail to check the natural nail C-curve. Then, look down the tip from the contact area and match the C-curves. Once you have chosen the correct tip, apply a line of gel adhesive to the free edge of the natural nail from sidewall to sidewall. Next, apply a line of adhesive to the center of the contact area of the tip. Slide the tip onto the nail plate at a 45° angle up to the stop point. Rock the tip onto the nail plate. Press and hold. The gel will fill in any imperfections in the nail plate and allow for complete adhesion. — Preuss
Try using a gel glue to fill on gaps that often cause bubbles. Then, hold the tip in place for about 10 seconds. — Martinez