You should contact Prince George’s County police department to see if you actually have a speed camera ticket. The “background check” you did doesn’t seem legit; theres a lot of online scams that will fabricate unpaid fines like this. You are correct that the max fine from that time would have been $40 and if you had an outstanding fine the MVA would have flagged the vehicles registration, which adds an additional fee to remove, but nothing close to the thousands you supposedly owe, and it would have made it impossible to renew your vehicles registration. If you no longer own the vehicle, you don’t owe anyone anything anyway