If you have authenticated successfully but you are getting a Please Enter a Valid Code error message then it's possible it's a timing issue:
The codes that are created on your authenticator app only last from 10-30 secs depending on the app. After this, the code expires.
If the time on your machine is not set correctly compared to verification server, then when you enter the code from your authenticator app it might show as invalid.
Your system should always be linked to Internet Time for the authenticator app codes to work correctly. You may need your IT provider to do this for you as your access to this may be blocked.
This process might also differ depending on what version of Windows you are using.
Windows 10 resync
Right click on the time and date at the bottom right of Windows.
Select Adjust Date/Time.
At the top right click Additional date, time & regional settings.
Click Set the time and date.
Click the Internet Time tab.
If you see the message This computer is set to automatically synchronize with 'time.windows.com, it means the time is not the issue and you should email [email protected] for assistance.
If you see the message The computer is not set to automatically synchronize with an Internet time server then continue with the setup.
Click Change Settings.
Click the checkbox beside Synchronize with an Internet time server.
You should now see the message This computer is set to automatically synchronize with time.windows.com.
Click OK and your clock is now synced correctly.
Log out of your booking engine account and log back in again.
Enter your code in the Reservation and your code should now work.
Note: If it still does not work please email [email protected] for assistance.