Are you logging in the same way you did before using the same account? If you logged in with a Nest account, use the "Sign in with Nest" link at the bottom of the login screen. If you login with a Google account, including if you migrated your Nest account to a Google account, use the "Sign in with Google" button. I'd also recommend checking you're looking at the right home using the menu at the top left of the app once logged in.
