OK, that's the problem I was expecting.
App Inventor projects are tied to the google address, so if you have a Google account with multiple addresses or the Google address changes, App Inventor will not be able to identify it as the same account.
I can transfer your projects from one Google address to another if that's what works best. I will need a private message with the old address, the new one, and some information about the projects in the account to help verify ownership.