AJAX subscribe box on my website works but still gives an error message

So i’ve checked & rechecked everything.
The URL and subscribe page ID is correct - url: ‘https://news.xxxxxxxxx.com/lists/?p=asubscribe&id=1
The list ID is correct - <input type="hidden" name="list[2]" value="signup" />

And it works perfectly, BUT I get the error message ‘Sorry, we were unable to process your subscription.’ every time somebody subscribes.

The ‘Request for confirmation’ email gets sent. It works when clicked on and the subscription is verified.

The only thing that is different is that jQuery is v3.7.0.
But it doesn’t work at all with any of the jQuery 1 versions. (And it completely breaks my site).

Any insights greatly appreciated.

@Simon66 You may need to set ACCESS_CONTROL_ALLOW_ORIGIN in the config.php file, see


Thanks Duncan, worked like a charm!
The final piece to the puzzle!