As I know, Coinbase uses the Authy app for 2FA until 31 march. They will no longer be supported after this date. If you do not migrate to Google 2FA or Duo, they will automatically remove the 2FA protection from your account.
Which time zone use on your phone, is there any difference in other devices which had regular access to Coinbase? it was a problem for me at one point until I put it on automatic time zone determination.