Sorry, I've no clue. Just wanted to point out there's also a plumbing forum here if you don't get any answers. Might try cross-posting there. Good luck!

Thank you. I did not know about the plumbing forum. How do I access the forum?

When you choose "Stories and Advice" from the top list of menu options, go to GardenWeb Forums and then on the left hand side, you have a list of forum options you can edit. Click Edit and scroll down to see all the options under Home (after all the Gardening ones).

You may also want to driop it in Home Repair. Or at least cross post it so that everyone see's the same post and responses.

Thank you - I will do that.

The pop-up is likely controlled by a lever that enters the drain tailpipe from the rear. A small ball seals the entry point when the cap is tightened. Reach around the drain tailpipe and feel the threaded cap. Undo the cap and release the ball and lever. Then you use the lever to fish around and find the extended tail of the pop-up, and cause it to pop-up. If the drain pull is stuck, you will likely have to undo a screw to release the lover lever.

Here's a video that explains some of it: https://www.youtube.com/watch?v=h24gBw0uJIM

I don’t have a lever. It is the type of plug that you push down to close and then push to open it. I would need to open the drain assembly to access it. I was wondering if there was anything I could try as I am not confident about opening up the drain under the sink. Thanks.

Most bathroom sink drain problems are caused by a moderately disgusting mixture of hair, grease, and soap scum. I haven't had to dismantle a trap or drain pop-up to deal with that gunk since I got a hair snare.

You just shove the business end of the gadget down into the drain, pull it back up, and wipe it on a rag (yuck). Do this in repeatedly, going around the pop-up, until it's coming back up mostly clean and, uh, please pardon the indelicate phrase, not so hairy. Then put the snare away and hit your drain with a kettle full of boiling water. That should take care of things for several months.

The link above is for information and example, and isn't meant to be an endorsement (though that happens to be the kind I have).

PS -- the package mine came in says it's for "single use." I can't imagine why. I've used it a least a couple dozen times, and it still works fine.

Thanks. This sink is only used for washing hands. I do have that gadget and use it for the other bathroom. I managed to get the plug out and the mechanism, and everything is clean. The mechanism does not seem to be working.