You likely haven't opened the chuck jaws fully before inserting the bit. It's an easy fix.
- Hold the front collar of the chuck with one hand and pull the trigger briefly in reverse. This will open the jaws.
- Insert your drill bit or driver bit all the way into the chuck, past the jaws.
- Now, hold the collar again and pull the trigger forward (drill direction) to tighten the jaws securely around the bit.
If that didn't work, there might be debris stuck in the chuck jaws. Clean them out with compressed air or a small brush. For a bit that's truly stuck and won't loosen with the chuck, don't force it by hand—you could get cut. Use pliers to pull it out.
Heads up: Always make sure the chuck is tight before starting any operation. A loose bit can cause injury or damage your workpiece.