ReCaptcha always asking for extra verification?

According to a WIRED article, Google is (amongst other indications) using IP addresses and cookies to recognize you.

Instead of depending upon the traditional distorted word test, Google’s “reCaptcha” examines cues every user unwittingly provides: IP addresses and cookies provide evidence that the user is the same friendly human Google remembers from elsewhere on the Web. And Shet says even the tiny movements a user’s mouse makes as it hovers and approaches a checkbox can help reveal an automated bot.

In your browser settings, you have most likely disabled third-party cookies, which will prevent Google from recognizing you. Add *.google.com to your whitelist, and the image-based verification won't show up again.

That's not a second verification. If your client's IP address is in google white-list, nothing will appear but the green tick. Otherwise they have to answer the security question.

It's not a bug, it's a feature!

For more information look here: https://www.funcaptcha.com/2015/01/06/recaptcha-is-still-vulnerable-perhaps-even-more-than-ever-before/