How to add an SSL to a subdomain.
1. log into cpanel
2. go to Security - SSL/TLS
3. Complete all 4 parts in order top to bottom:
4. go back to Security - SSL/TLS Status:
5. click on Run AutoSSL:
6. after a few minutes, when run is finished, you will see:
7. self-signed FREE SSL has been installed on your subdomain.