Stopped paying property tax on vacant land. In 2 years county will certify property to state. 2 more years auction at tax sale. Land will not sell. When can I claim loss.

You cannot claim the loss until you have lost all rights to the property through a tax foreclosure auction.

High volume of vacant land in same "retirement" area all going thru tax sale foreclosure auctions. No vacant land is selling. My property will go to auction but likely will NOT sell. Will I never be able to claim a loss?

If you bought this land to build your own retirement home, then no, that personal loss will never be deductible.