Failed request with 403 response status on iOS on production

On domain when making a request to the server with expected status 403 the request fails. Only on iOS. On UAT environment and local everything works as expected. The error is Error Domain=NSURLErrorDomain Code=-1206 “The server “” requires a client certificate.”

But the certificate is added, otherwise all requests will fail regardless of the status. The only one difference between UAT and production is that there is a Cloudflare added.

Is somebody meet something related?