Best way to trigger an APA for client with poor communication and understanding

We have a client who we are trying to help with a number of issues. He has claimed UC but is really struggling to understand that his housing costs are included in his UC payment. He just can’t grasp the concept of this and can’t see why he should give his money to the landlord. He is very vulnerable and already in arrears. The landlord doesn’t seem to be doing anything except putting pressure on the client (although this is difficult to tell given his problems expressing himself and with understanding). What would others think is the best approach here - try and speak to the landlord to get him to ask for a UC47 or is there some way of us triggering this directly as advisors.