Below is an example of this error:
"...has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource."
Usually this CORS error happens when a site does not have the SSL certificate, or HTTPS.
We suggest that you update the site with HTTPS, because it is a well-recognized security measure in the market and services like this one: https://letsencrypt.org/, are free, with no downsides.