Push pop up drains could stick if they are not used often. This is usually due to a buildup of soap scum, calcium from hard water or, mold. Here are some tips to get it working again.
First, you need to remove the cap to gain access to the stem.
If you can get the plug cap in the open position you can grip the outside with your fingers or carefully with pliers and rotate it counter clockwise to remove. (If using pliers, you may want to protect the cap with a rag to prevent it from being scratched)
If the plug is jammed in the shut position, push down on the top surface while trying to rotate counter clockwise. Usually, it will come apart easily. Wearing rubber gloves could give you more grip.
Use needle nose pliers to turn the stem counterclockwise and remove. You may be able to remove with just your fingers.
Clean as thoroughly as possible using a rag, wire brush, etc.
Soak the stem in a solution like CLR or vinegar for 15 minutes to break up the soap or calcium buildup. Rinse in hot water. Open and close the stem actuator to ensure it is working smoothly.
Spray with silicon spray or WD40.
Reassemble in the reverse order. You do not need to overtighten, just make snug.
Operate it a few times to make sure it functions
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