Really Worried about my brother

My brother is 38 and lives alone in rented accommodation.  Our mother passed away 2.5 years ago and was his primary cater/company.

he can function independently from a physical point of view, but has become extremely withdrawn and isolated.

he does not let us visit, is not leaving the house and has no contact with anyone.

care workers have not been responding to emails and he is back to the bottom of the waiting list as he told them he is fine- atypical answer from the world of anxious folk with autism.  

any advice of where to Get help please???

he is now not answering texts or the phone and I am scared.

thank you