The hostname attached to that site is not pointing to our CDN. This is what a DNS lookup returns (I’ve hidden the hostname since you seemed to want it hidden):
$ host YOURHOST
YOURHOST has address 172.67.207.46
YOURHOST has address 104.27.152.70
YOURHOST has address 104.27.153.70
YOURHOST has IPv6 address 2606:4700:3036::ac43:cf2e
YOURHOST has IPv6 address 2606:4700:3032::681b:9846
YOURHOST has IPv6 address 2606:4700:3031::681b:9946
Seems like that is pointing to cloudflare, who will have to manage SSL for you. If you configure as mentioned here instead, then we can get SSL: How to Set Up Netlify DNS - Custom Domains, CNAME, & Records
Note that using cloudflare as a proxy to netlify is a bad idea as described here, so the second solution I mention (configuring to point to us without proxying) is preferred: