Unknown error (invalid-json). Please contact an administrator for more info.

I am also having the exact same problem. By disabling the plugin I have managed to login however I am hoping this problem can be resolved as I otherwise rate this plugin highly.

Tania

Also having this problem. I have to disable the plugin to log in.

Any luck with this issue? I am getting the same error
Unknown error (invalid-json). Please contact an administrator for more info.
on my site with Contact Form 7

I think the plugin is abandoned. I just uninstalled and switched to something else. I think Contact Form 7 has something else that works natively now, so you should just use that.

I agree with @brianjohnsondesign in that the plugin has been abandoned. I uninstalled it and use a different plugin now too.

Thank you, I will also delete the BWP reCAPTCHA plugin and move to another reCAPTCHA plugin

I seemed to have solved the problem by selecting the Request Method (on the plugin settings page) to cURL.

Not sure if this will work for others, but it maybe a start…

I solved this by moving the plugin to another folder using the Linux command line, effectively disabling the plugin

sudo mv /var/www/wp-content/plugins/bwp-recaptcha /tmp

Just to confirm, I temporarily disabled the plugin by moving it, logged in, re-enabled it and then changed it to cURL. Seems to be working perfectly fine.

I changed to Curl and every thing is ok now.

FOR A SIMPLE FIX: Go into your file manager and rename the bwp-recaptcha folder. WP-Content>Plugins> to something like bwp-recaptchaXXX

Refresh the login page and all will be welll