I’m not too sure why you can’t login at all, at least using your WordPress username/password, but perhaps you have the option ‘automatically redirect to google login’ enabled for the plugin.
Please try accessing your site by adding this to the link to your site URL:
/wp-login.php?gaautologin=false
That will stop automatic login via google, so perhaps you can use your normal WordPress username/password at that point.
If you can access the admin panel, you can then disable the option ‘automatically redirect to google login’ under Settings -> Google Apps Login.
Then you would need to follow the instructions to configure Google Apps Login again – perhaps you missed something the first time.
If you can’t access at all via the above link, then I’m afraid you may need to find a way to access your WordPress database directly – perhaps I can help you find a guide on the web if it comes to that.
Please let me know how you get on, and if you still have problems please explain in more detail what is going wrong – why your Google login doesn’t work, why your WordPress username/password isn’t being accepted etc.
Email [email protected] with any further information, as that is the best way to reach me.