Captcha provider certificate error

[Tripredacus]

The captcha provider on the site/forum's registration form is showing a certificate error for some users. The result is that the captcha does not appear on the form so the registration process cannot complete.

Failed to load resource: net::ERR_CERT_COMMON_NAME_INVALID for cap.js (remotely hosted by keycaptcha.com)

Reported to me by a user but they did not provide system configuration. I verified using SRWare Iron 135.0.6850.0 on Windows 10 21H2.

[Karla Sleutel]

Tripredacus, the user could be from a troublesome location, Nigeria, Russia, Uganda, whatever. I tried to make an account, they simply asked me for a word.

I didn't even have to solve captchas. Though, there is an error in the word colour, a misspelling.

[Tripredacus]

Color is spelled correctly, at least in US English it is that way. The sentence has a grammar error but that's probably even better to deter bots, idk. 

Something is supposed to appear next to Security Check and it doesn't, not even for me. I suppose it could appear if you modify your browser settings to allow such content to appear but that shouldn't be a requirement, the forum's registration should work on stock (and "secure") browser settings.