Getting “Please solve Captcha correctly” Error Always (v2 tickbox)

Hi,
I use this plugin for multiple websites and it works fine in all websites.

But I’m getting an issue in one of my new website. I’m using version 2 tickbox captcha.

I can’t login (on the admin page). The captcha always gives an error. I get the green tick but after pressing log in, I get an error “Please solve Captcha correctly”.

This doesn’t happen on any other website and I can’t seem to understand the issue.

Can this issue be solved?

The page I need help with: [log in to see the link]