Tax harvesting and trying to take loss for YNDX. How?

I have some signficant gains this year and looking to find as many losses as possible.

I own YNDX but it has zero value. I want to use as a loss. But how do I do that?

I normally just sell. I have the shares on Schwab and do not have any way to sell them.

I called Schwab and they were not much help. I will call again later today and see if I get a better rep on the phone.