Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. https://crt.sh/?q=example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.
Free SSL for free subdomains is not available at this time. In addition to the limitations covered above, Let's Encrypt enforces strict limits on how many certificates they will issue for each registered domain name. Since domains like epizy.com and rf.gd count as a single registered domain, very few certificates can be issued for free subdomains. Because of that, we have chosen to not issue free SSL certificates for free subdomains at all.
We're currently working on a way to get free SSL on free subdomain as well. But until that option is ready, you cannot get free SSL for free subdomains.
It looks like unless you get your own domain name, you won't be able to.