How to add certificates to a Domain Name

[CB57]

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.

My domain is dinetechcb.dyndns.org

I ran this command: router.dinetechcb.dyndns.org

It produced this output: certificate is only good for dinetechcb.dyndns.org

I want to know how I can add a certificate for router.dinetechcb.dyndns.org since I have a valid certificate for dinetechcb.dyndns.org.

My Synology VPN works fine on Chrome (not accepting the certificate as secure), but Firefox will not accept the URL stating that the certificate is only good for dinetechcb.dyndns.org.

Hopefully this makes sense and someone can help.
Thank you in advance,
Tom

[danb35]

@CB57

I ran this command: router.dinetechcb.dyndns.org

That isn't a command.

@CB57

It produced this output: certificate is only good for dinetechcb.dyndns.org

Whatever you did to request that certificate, do it again, but add router. to the request. With the absolutely nothing you've told us about your setup, that's the best I can say.

[CB57]

Now that you put it that way, you’re right. DYN will not let me create a host with a “period” between router and dinetechcb. Synology creates the VPN login name with the period. Not being proficient in Let’s encrypt, I thought I’d ask for help. I guess I’m not even proficient enough to ask a question.
Thank you for your response.
Tom