If your Google Authenticator code isn't being accepted, it's usually due to one of a few common issues. Try these steps in order:
1. Sync your Authenticator's time (most common fix)
If your Google Authenticator code isn't being accepted, the cause is almost always a small time-sync issue between your device and our servers. See How to Calibrate Your Phone's Time to fix it.
2. Make sure you're entering the code in time
Each code is valid for about 30 seconds. If the timer is nearly up, wait for a new code to generate and enter that one. Don't reuse a code that's already expired.
3. Refresh and try again
Reload the login page and enter a newly generated code.