Do you get an error that looks as follows:
The cPanel Store returned an error (X::PermissionDenied) in response to
the request “POST ssl/certificate/free”: This partner does not offer
free 90-day certificates
In some instances, you may not be able to obtain the free AutoSSL certificate, or the free Hostname SSL certificate, or even purchase an SSL certificate.
Your provider may have disabled this option for your server. If so, you would need to discuss that with them directly. There is, unfortunately, nothing that can be done on the server or by cPanel, L.L.C. to enable this feature.