reCAPTCHA – “Please complete the security check again”

I have enabled the reCAPTCHA check on a live site, and no matter how many times I follow the steps, it always reloads the registration page with the “Please complete the security check again” error message. I have tested it countless times on multiple browsers and devices, and it simply seems to be broken. Has anyone else experience this constant error, and how can I get this working?

The simple math method works, but spam bots seem to easily outsmart it which renders the option pointless.