This situation can be caused by many factors. What you can do is:
1. Make sure you’ve updated your 2FAS app to the latest version.
2. Make sure that you didin’t delete a code/token assigned to the service – you can do it by looking into your Trash. If you did delete this code/token, just restore it and try again.
3. Despite our app working offline, it requires a correctly synchronized time to work. If your device doesn’t use internet settings to set the time, make sure that you are connected to the internet for time synchronization via the 2FAS app, and then try retyping the code.

If none of the suggestions worked, you probably saved an incorrect private key on the website, and you need to do it again. Contact the website support and ask them to help you with that.