Please try the following:
On Android:
- Go to the main menu on the Google Authenticator app
- Tap More Settings.
- Tap Time correction for codes.
- Tap Sync now.
- Enter your OTP code in the Two-Factor Authentication box.
On iOS (Apple iPhone):
- Go to the iPhone Settings App (your phone settings area)
- Select General
- Select Date & Time
- Enable Set Automatically
- If it's already enabled, disable it, wait a few seconds and re-enable
- Enter your OTP code in the Two-Factor Authentication box.
If you are still having 2FA trouble after doing the above please email pool@bitcoin.com