SSL & subdomain confusion

Unless you have a wildcard certificate (expensive), you cannot have SSL with subdomains.

SSL will normally only work with the base primary domain on the account.

So if you wanted to have say "http://pizza.mydomain.com" and assuming "mydomain.com" is the
root main domain on the account then the correct way to call that address in SSL mode would be
to use the base domain like this "https://mydomain.com/pizza/".

Don't use subdomain while using SSL, use the subfolders. When non-SSL can use the subdomain names

If you want subdomain for both SSL and NON-SSL, you either have to get a wildcard certificate or you will
have to put each subdomain on it's own Cpanel account and it's own distinct IP and get a unique SSL certificate
for each subdomain that you use so you options are either expensive or complicated.