Server auth token not refreshed after restorePreviousSignInWithCallback

Our app currently uses the server auth code to exchange for a token on the backend in order to get the google user id and from that the app specific user account. After we exchange this code on the backend, it is no longer valid and we cannot use it again.

On Android, our client will always give a new server auth code when the user does a silent sign in on app launch, but on iOS it seems to only provide the server auth code from the previous session. (via restorePreviousSignInWithCallback)

I was wondering if there is a way to force this to refresh so that we can get a valid server auth code (one that hasn't been used already)? Or am I perhaps thinking about the flow of this incorrectly?

Thank you