UE is not out of business as far as parts that are in stock. I just received some drive train parts that were ordered less then 5 days ago.
The mono block extension I believe has been out of stock for several months and if it was out of stock when you ordered its very doubtful that any will be made anytime soon, if ever.
Was your CC charged for the item? If so, I would continue to send emails and even post a question to Robin on the UE forum.