When trying to sync Google calendar with my users account, I receive this message: 

Por el momento, el acceso con Google no está disponible para esta app Google todavía no verifica esta app para que sea compatible con "Acceso con Google".

translation would say something like: for now Google access is not available for this app, google hasn't verified yet to be compatible with "Access with google"

The problem is that we have 25 users and 20 of them have already linked their accounts, I only have problem with 5 of them