A: Please be aware that Authenticator Apps refresh frequently.
Make sure you are using the most recent 2FA code from the application.
An issue with 2FA could also be because the time on your Authenticator app is not synced correctly.
If you are using Google Authenticator
To make sure that you have the correct time in Google Authenticator:
Go to the main menu on the Google Authenticator app
Tap More and then Settings.
Tap Time correction for codes
Tap Sync now
On the next screen, the app will confirm that the time has been synced, and you should now be able to use your verification codes 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.
If that doesn't work, try removing the account from Google Authenticator and adding it back using the QR code in your welcome email.
If that still doesn't work, you could try using an alternate Authentication App.