Why is my drain stopper stuck and how can I fix it?

Your drain stopper may be stuck due to a buildup of debris or corrosion. To fix it, you can try using a plunger to dislodge the stopper, using a drain snake to remove any blockages, or applying lubricant to help loosen the stopper. If these methods don't work, you may need to unscrew the stopper assembly and clean or replace it.