Your tenants can only make a new claim for Housing Benefit if: 

• A single person is of state pension age. Or if they are part of a couple and at least one of them was state pension age on 14 May 2019.
  You can find the Pension Credit qualifying age using Check your State Pension age
• You provide them with supported accommodation
• They have been placed in temporary accommodation by the Local Authority

If not they need to claim Universal Credit.