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

Your bathroom sink stopper may be stuck due to a buildup of hair, soap scum, or debris. To fix it, you can try using a plunger to dislodge the blockage, using a drain snake to remove any obstructions, or using a mixture of baking soda and vinegar to break down the clog. If these methods don't work, you may need to remove the stopper and clean it manually.