Sold condo in back in 1998 and recently found out property taxes are still in my name for that unit? Why would that be

There are 2 possibilities I can think of:

(1) The deed you gave to the buyer was never recorded in the county clerk or county register's office.

(2) The sale information was never sent by the county clerk to the tax assessor.

You can go to the clerk's office and see if the deed was recorded. If so, get a copy of the recorded deed and provide it to the tax collector. If the deed was not recorded you will have to get back in touch with the people who handled the closing. You may have to contact the person you sold it to and have them contact their title company.