"Please enable cookies" in XHR response

Hi, and thanks for let me partecipate in this community. I’m Salvo, developer from Italy. I have an Ajax contact form (Preventivo sito internet - Quiky). When I submit the form, the XHR fails with code 500 and the response page shows many Cloudflare messages like “please enable cookies” and “DNS points to prohibited IP”. Cookies are enabled on browser and the same dns IP is used to serve the the website, so it’s a problem related only to XHR request. Any ideas how to solve this? Any help is appreciated, thanks.

got a 403

Try clearing browser cache as the first step.