Subdomain added, but on website I see only sub.mydomain.com server IP address could not be found

[rbm]

I added subdomain. It was created. In public_html folder there is a folder for my subdomain.
In DNS my subdomain is added too as record A with IP like for domain 77.xxx.xx.xx
When I try open my subdomain addres in webbrowser I have error:
sub.mydomain.com server IP address could not be found

Domain works and I can open webpage by url with main domain.
I have https. But subdomain doesn't work for http and https.

I read that maybe I have to configure wildcard. But I don't know how.
In httpd.conf I have configuration for my subdomain:

1. <VirtualHost 77.xxx.xx.xx:80 >
2. ServerName www.sub.mydomain.com
3. ServerAlias www.sub.mydomain.co sub.mydomain.com

And for https section:

1. <VirtualHost 77.xxx.xx.xx:443 >
2. SSLEngine on
3. SSLCertificateFile /etc/httpd/conf/ssl.crt/server.crt
4. SSLCertificateKeyFile /etc/httpd/conf/ssl.key/server.key
5. SSLCACertificateFile /etc/httpd/conf/ssl.crt/server.ca
6. ServerName www.sub.mydomain.com
7. ServerAlias www.sub.mydomain.com sub.mydomain.com

 

[factor]

Did you wait for the DNS to propagate? It can take up to 24 hours.

 

[rbm]

The main domain was visible after short time maybe one hour. Subdomain was created a couple of hours age and still is the same message.