Recently I come across an issue on my WordPress website where I can not able to login to the admin site. Website Users can not able to add comments on posts. The error I got is as following
Error: Google reCAPTCHA verification failed. You are probably not a human!
This error is caused by a plugin “Simple Google reCAPTCHA“. I got this error multiple times and I fix it by following two solutions.
Solution 1
If you are using Google Chrome and your WordPress website is displaying Ads. Please make sure you are allowing 3rd party cookies. You can disable the third-party cookie blocker by clicking on eye icons as shown in the following screenshot.

Solution 2
if the above solution can not resolve the issue then you need to disable all plug-ins from the WordPress database, Login to the admin site, and enable plug-ins one by one except the “Simple Google reCAPTCHA” plug-in.
You can do that by following the below steps
Login to Phpmyadmin to explore WordPress Mysql database tables
Search for table ends with _options and click to explore it
Search for the row “active_plugins” and click on edit

In the next screen, delete everything in “option_value” column and click ‘Go’ to save the change.
Now you should be able to log in to your WordPress admin site.