We have a web app that uses OAuth to sync user's gmail account asking for some credentials. Now since last week we are getting this message that "sign in with Google is temporarily disabled for app" but we haven't changed anything from our settings at all. Also we have everything approved and configured because it was working fine before that time.
You need to follow the process described [here][1] to request verification for your app.
[1] https://support.google.com/cloud/answer/7454865?hl=en
Also see https://gsuite-developers.googleblog.com/2018/06/new-oauth-protections-to-reduce-risk.html