I am going through the exact same experience. Developed a store for a client, ready to transfer ownership and it gives me the same error. Been over a week reaching out to support multiple times a day and getting the same response every time.
This is very frustrating as this has been months of work and now a business is on standstill until it can be resolved, but they are not offering any resolutions. Years working with Shopify and this is the first time I feel let down by the platform and their team.