If a wildcard subdomain is added to a cPanel account and the SSL has been deleted for it (or otherwise there isn’t a secure vhost for it), SSL/TLS status displays this message:

No certificate available. AutoSSL does not support explicit wildcard 
domains. You must purchase a certificate to secure this domain.

When Let’s Encrypt is enabled, AutoSSL supports explicit wildcard subdomains so this messaging is not accurate.

Ignore the message, troubleshoot AutoSSL errors as needed.