Under some circumstances, AutoSSL may fail to issue an SSL certificate for your Addon Domain. When you check the SSL/TLS Status page in cPanel for the Addon Domain, it cannot be found.
This is a result of important entries missing from the
serveralias line in the userdata files. When an Addon domain is created, it is always associated with a subdomain of the cPanel account's main domain. userdata files are created for this subdomain. For example:
Within these files, the following line is automatically generated:
serveralias: mail.maindomain.tld addondomain.tld www.maindomain.tld www.addon.maindomain.tld
If any of these entries are missing they need to be added again. How this line becomes modified may vary on a case-by-case basis.
serveralias line does not contain entries for the addon domain itself, or its mail and www subdomains, those need to be manually added back to the file using a text editor such as vi or nano. It is advised to create a backup of the file prior to editing it.
After editing the file, you then need to rebuild the Apache configuration and restart Apache: