You seem to have several issues, you need DNS resolution to have smart licensing work, either cloud or satellite SSM (as well as necessary ports being open).
The server itself is recommended to have FQDN, but it's not mandatory, that's a separate problem.
Yes, if you change/add the domain name from the server(s) all the certificates will be regenerated as the CN from the certificate is either the hostname or the FQDN.
There is documentation that explains the exact steps to follow for domain name changes, it has to be followed to the letter to avoid any issues. If you were using CA signed certificates they'll have to be signed again, if you had secure communication with other systems and you exchanged certificates, you will need to do so again (if using self-signed or changing the CA)
HTH
java
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