Enable AutoSSL (Let's Encrypt) in cPanel

Step 1 - From cPanel, select SSL/TLS Status

Step 2 - Make sure the boxes are ticked for the domains/subdomains you want a SSL for and click Run AutoSSL

Note 1: You may have to wait 3hr for the free SSL to apply
Note 2: If under the list of domains, the chosen domain/subdomain has + Include during AutoSSL under the Certificate Status, available, make sure to click that first.