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. crt.sh | 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: http://matter.kai.com
I ran this command: certbot --nginx -d matter.kai.com
It produced this output: Certbot failed to authenticate some domains (authenticator: nginx). The Certificate Authority reported these problems:
Detail: DNS problem: NXDOMAIN looking up A for matter.kai.com - check that a DNS record exists f or this domain; DNS problem: NXDOMAIN looking up AAAA for matter.kai.com - check that a DNS record exists for this domain
Hint: The Certificate Authority failed to verify the temporary nginx configuration changes made by Certbot. Ensure the listed domains point to this nginx server and that it is accessible from the internet.
My web server is (include version):
The operating system my web server runs on is (include version): red hat 8.7
My hosting provider, if applicable, is:
I can login to a root shell on my machine (yes or no, or I don't know):yes
I'm using a control panel to manage my site (no, or provide the name and version of the control panel):
The version of my client is (e.g. output of certbot --version or certbot-auto --version if you're using Certbot): certbot 2.5.0
If you create your own DNS server and add kai.com to it, that doesn't mean you own kai.com.
Let's Encrypt uses the real world DNS hierarchy to determine who controls a domain name. I think, based on your posts so far, that somebody else owns the domain. You cannot have a Let's Encrypt SSL certificate for a domain that you do not control.