I'm having the same problem described in the question below:
The shared board I'm trying to reopen: https://trello.com/b/Bv8lY0Jn/kanban
The board administrator no longer has access to the email they used to register on Trello, making it impossible to recover the password or reopen the board from their account. If you can make me an administrator, I will be able to reopen it.
Could you please add me as admin of this board?