Does this issue occurred when you created the flow or when you are switching connection?
I used my own email in the beginning then switched to a dedicated bot email, and I encountered the exact same issue.
I used a different trigger (When a new email arrives), but the problem should be the same.
The Folder property (Inbox) is tied to the current connection (email address), and will stay the same even if you switch to another connection. So, if you switch the connection to another email, the trigger is going to fail because it cannot find the old inbox in the new email.
The "Mailbox move in progress" is likely a guess, because from a program's view, it tries to find an inbox that doesn't exist in the current email, so it think that theres a mailbox move in progress. The real problem is the "Cross server access is not allowed", as you are trying to access the old mailbox in the new email.
So the solution is simple, re select the inbox.
Even your problem is not caused by switching connection, I would still recommend updating the folder property, since it is known to be buggy.
