Sorry, my fault, I forgot a thing: Cloudflare, by default, only secures your root domain and the first subdomain level. In this case elgatoproductions.net and *.elgatoproductions.net. You’d need to purchase a certificate containing www.illustration.elgatoproductions.net or *.illustration.elgatoproductions.net from Cloudflare for that.
A cheaper alternative would be to disable Cloudflare proxying for this DNS record (set it to DNS-only, which also disables most Cloudflare functionality for that one) and use a CA like LetsEncrypt to secure this domain. Keep in mind that it’s not automatically managed by Cloudflare in this case.
At the moment, Cloudflare does not return a certificate for this subdomain.
Here’s a link to the support page with information about Cloudflare’s custom hostname SSL certificates. You’d need the $10 one if you want to go with the first solution: