With my Enterprise account I received this message 40 minute ago from the Google Cloud Platform support, API team:
Recently the Drive engineering team implemented new daily upload quotas on a user account basis, once these limits are hit they take 24 hours to reset. The Drive engineering team do not make their limits public and limits are subject to change at their discretion. Support have not been informed of the limit however recent cases indicate that it is indeed a 750GB daily upload limit per user account.