Invalid Captcha Response

Using Elementor on the website, I was previously displaying the sign up form using the Automatic Output on a homepage popup. When the Invalid Captcha Response error started cropping up, I switched to linking it to a page which contains the sign up form (this worked, so it appears it was having problem with the popup element of Elementor).

When the official plugin came out, I used it in the hopes that it will solve the problem (as I really wanted the sign up form to be on the pop up itself for convenience). It did, for a time. Now the Invalid Captcha Response error has started up again.

I use the same sign up form for multiple websites, same issues are experienced across the board. And yes, the domains have been entered into the Settings page of the form.

Can anyone help me figure this out?