i've had this same issue, checked the IAM admin and none of my projects are pending deletion. i've contacted support, but i found a solution that may be indicative of what the problem is.
normally, I'm logged into two different Google accounts, my work (default) and my personal (authuser=1). when going to `
console.firebase.google.com?authuser=1`, the legacy projects that are associated with my personal email show up, but none of the accounts that have been migrated (they're active in the Firebase CLI). attempting to route directly to the project URL results in an error, even after adding the `authuser=1` URL.
however, when I made my personal account the default (thus absolving the need to add the `authuser=1` flag to get the application to route properly), the projects show right up and are accessible. might want to give that a try if you're having trouble accessing those projects.