The business portfolio id is used as part of the URL for Facebook Business Centre, so I replaced the id for a business centre I had access to with the problem business portfolio. Fortunately they still had access to that business portfolio and could accept the request to disconnect that page from the old portfolio, opening it up to joining a new one.
This only worked because they had access. We would still be stuck if it was controlled by someone else
What did you try that they didn’t, if you can share?
What I think confused them is the Business Portfolio had a similar name to the page, so maybe they didn’t realise there was a difference.
On this page you can see who has access and what business portfolio a page is under https://www.facebook.com/settings/?tab=profile_access
The business portfolio id is used as part of the URL for Facebook Business Centre, so I replaced the id for a business centre I had access to with the problem business portfolio. Fortunately they still had access to that business portfolio and could accept the request to disconnect that page from the old portfolio, opening it up to joining a new one.
This only worked because they had access. We would still be stuck if it was controlled by someone else