Although this court has not previously addressed whether lack of registration under Section 29-105.02 can be forfeited if not timely raised, we have treated a very similar defense as "waived" because not timely raised. See Tenants of Minn. Gardens, Inc. v. D.C. Rental Hous. Comm’n, 570 A.2d 1194, 1196 (D.C. 1990) (tenants "waived" defense that landlord lacked certificate of authority to do business in D.C., by failing to raise defense before administrative agency; "In cases where a party brings an action which it has no legal authority to file, … a court will not void the proceeding after the fact. In such cases, the opposing party must ordinarily bring the defect to the attention of the court at the time the action is filed.").