CloudFlare has a setup that uses their own IP's to proxy the address you are using. In short, they replace your IP with one of theirs. In order to get your CNAME record set up correctly inside Cloudflare, you need to bypass their server and make secure.pageserve.co the active CNAME record, as Cloudflare makes the domain appear as an A record.
If your current setup looks like this, you will have to click on the blue Edit dropdown and disable the default proxy from the orange toggle in order for the cloud to become grey/DNS only.
It will look like this after the change:
Important notes:
1. If the CNAME is proxied in Cloudflare, you might see an error: Error 1014 CNAME Cross-User Banned. You will need to bypass Cloudflare's proxy, as shown above, in order for the page to be shown live.
2. If point 1 is done, but the error still persists, please make sure that you have already published a page on that specific subdomain, as this will help our system identify that the subdomain is in use, it will try to apply the SSL and thus will solve the error.
3. If all of those have been done, but the error is still there, you can contact our Support Team at help@instapage.com, as we might need to manually push the SSL for you.