[Updated 2.2024]
It may seem weird but from time to time, the verification codes from your Google Authenticator app (Google 2 Factor Authentication app / Google 2FA app) may not work like they used to.
This is likely due to a time synchronization problem that may happen from time to time due to the nature of mobile phone networks and the Google Authentication app.
You will need to perform a TIME SYNC.
This is what Google says about this:
You can refer to Google's help page about this here:
https://support.google.com/accounts/answer/2653433?visit_id=636735803516007086-2349741641&p=timesync&rd=1
Once you have performed the TIME SYNC on your Google Authenticator App, the verification codes generated by it should work well again.