@Alex T. Notifying interested parties about the pending case to foreclose the right of redemption is the essential step in your tax sale litigation that will leave you with a defensible title or one that is subject to attack.
Your attorney should have the notices served on the interested parties and posted and mailed to the property address. In the case of an expired entity the court will sometimes allow you to serve the Dept. of Assessments and Taxation, make a serve by publication in the courthouse, etc. But you have to get permission from the court to serve that way by documenting the unique facts of your case to the court.
My tax sale property we found out the owner was deceased right after we got our first judgment. So I hired a second lawyer to open her estate (as its largest creditor), once the estate was opened we served that lawyer and we got a new judgment that will (hopefully) survive any potential claims from her heirs.
The lien is still valid, the defendant will owe all the interest and your reasonable costs and fees should they elect to redeem the property.