Limited Partnership Lossisyributions

My husband invested in an Oil & Gas Limited Partnership which has had no activity/distributions since 2018 but apparently is still in existence/not filed a final tax return because we continue to receive Schedule K-1s (which shows No Activity).  At what point can we claim a deduction for a worthless partnership interest/Loss from Investments on Form 8949, or do we have to wait for the Partnership to file a final Tax Return?