I have opened several @gmail accounts ... in each realative Google Cloude I create service accounts. Using Python I do some checks and some give storage space (15gb - be careful I am not confusing 15gb made available for @gmail account is 15gb made available for service account) and some do not.

I can't explain it, on some I can use service accounts (and I have 15gb available) on others I have to necessarily use OAuth Client IDs because the Gb available is 0 so I can't do uploads and other operations.

I have opened many @gmail accounts between me, my friends and some of my clients, done dozens and dozens of tests some work (always have 15gb available), some after a while stop working (the 15gb quota goes to 0) some just don't work (always have 0gb quota). On all accounts at most I used to upload some txt files