Why is the root certificate returned after transferring a certificate for a subdomain?

Question

Nginx

Greetings.
There are two servers (one for a subdomain, another for the main one). We combine them. Transferred the certificate, but the browser says that the root certificate is returned on the subdomain.
This may be due to the fact that I go to the subdomain by editing the hosts, but the A-record of the subdomain still has a different IP?
I think that because of this, but it’s silly to transfer completely without being sure, and there’s nothing in the handshake charts about IP (((
Thank you for your attention.

Answer 1

In sense there were two machines, for the domain and a subdomain, and the economy from the second moves to the first?
In theory, if a subdomain certificate was returned on a valid subdomain, then it should now; hence the root certificate on the subdomain is given exactly on the "moved" installation.
Accordingly, in the nginx config, it should be server{…}under the main domain (with paths to the domain certificate/keys), and server{…}under the subdomain (with paths to the subdomain certificate/keys).