I have the same issue. I can not login if reCaptcha is enabled in the security tab. reCAPTCHA is working fine otherwise on the wordpress login page. It all has worked before some recent updates. All my plugins are updated. Not sure when it all stopped working as this site is relatively new and not that busy at all. A customer just contacted me today that she can not login anymore. It’s working now after disabling reCAPTCHA. What is going on? Please help. Let me know if you need more info.