Built-in Math: You must complete the CAPTCHA form

Hi,

That form seems to be from the WP Members plugin and they are handling it using custom code it seems. They might be calling the normal login form hooks, hence the captcha is getting printed, but not submitting the captcha challenge input to the authentication function, as they don’t know about it, so when Advanced Google reCAPTCHA gets to checking the captcha it’s not submitted so it marks it as failed.

WP Members seems to have it’s own reCAPTCHA integration so you should probably try using that instead https://rocketgeek.com/plugins/wp-members/docs/registration/using-captcha/