I am trying to use your catcha - with correct (just registered) google captcha keys - but during login I see an error saying invalid keys and I cannot login because of it.
It seems you've configured keys wrong.
Please try to generate keys again. Delete keys, make sure you don't have other reCAPTCHA plugins. Click on this link and generate new API keys:
Create a new API. Make sure you copy the correct key to the correct field. Make sure you don't insert extra spaces before or after keys.
The video provided above should help you: https://www.youtube.com/watch?v=eFgD_txPic0