nginx wordpress sub-domain lets encrypt - wordpress

Question

I ran wordpress site with this SSL tutorial. https://www.digitalocean.com/community/tutorials/how-to-secure-nginx-with-let-s-encrypt-on-ubuntu-16-04
I have example.com domain. and I create test.example.com sub-domain.
There's problem with connect with test.example.com it shows NET::ERR_CERT_COMMON_NAME_INVALID on chrome.
How can I connect sub domain to existed lets encrypt. and
further more, How can I connect second-domain example2.com to SSL.

Answer 1

As stated in Let's Encrypt FAQ Let’s Encrypt doesn't offer wildcard certificates:
Let’s Encrypt offers Domain Validation (DV) certificates. We do not
offer Organization Validation (OV), Extended Validation (EV), or
wildcard certificates, primarily because we cannot automate issuance
for those types of certificates.
If you have requested certificate just for example.com it won't work for www.example.com or test.example.com.
You need to explicitly declare every domain or subdomain in your request using -d parameter of letsencrypt or modern certbot:
letsencrypt certonly -a webroot --webroot-path=/var/www/html -d example.com -d test.example.com -d www.example.com
You can request certificate for different domains the same way:
letsencrypt certonly -a webroot --webroot-path=/var/www/html -d example.com -d www.example.com -d example2.com -d www.example2.com

Answer 2

What is your settings on your nginx server directives?
The server directives for both port 80 and port 443 should be refer to the subdomain instead of your domain. Like this:
server {
listen 80;
server_name subdomain.example.com;
return 301 https://subdomain.example.com$request_uri;
}
server {
listen 443 ssl;
server_name subdomain.example.com;
....
}
As for your second domain example2.com, it depends on what you purchased is single-domain SSL certificate or multi-domain certificate.