If your (Google) Authenticator codes are not working, make sure your device’s date and time settings are correct, as the app may not function properly if the time isn’t synced.
Here’s what you can do:
For iPhones
Go to Settings on your iPhone.
Scroll down and tap General.
Tap Date & Time.
Make sure Set Automatically is turned on. This will sync your device’s time with the network and help ensure it matches the time used by the Google Authenticator app.
Unlike Android, there isn’t an internal sync option for the time in the Google Authenticator app itself on iOS. The app relies on the system time, so ensuring your iPhone’s time is set correctly should resolve issues with code synchronization.
For Android phones
To set the correct time:
On your Android device, go to the main menu of the Google Authenticator app.
Tap More : › Settings › Time correction for codes › Sync now.
On the next screen, the app confirms the time has been synced. You should be able to sign in. The sync will only affect the internal time of your Google Authenticator app, and will not change your device's Date & Time settings.