Symptoms
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.
Description
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:
/var/cpanel/userdata/$cpaneluser/addon.maindomain.tld
/var/cpanel/userda/$cpanel/user/addon.maindomain.tld_SSL
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.
Workaround
If the 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:
/scripts/rebuildhttpdconf
/scripts/restartsrv_httpd