2 servers, 2 cpanels, 1 whmcs

I created two servers:

1. host.mydomain.com
with nameservers:
ns1.mydomain.com
ns2.mydomaincom

on the same server I instaled wmhcs which will be resbonsible for creating new accounts on another servers.

Now I created second server:
s1.mydomain.com,
which runs fine.

Now I can created cpanel account with wmhcs (which is installed in host.mydomain.com) on s1.mydomain.com

I created one account on s1.mydomain.com with a domain: myseconddomain.com. For myseconddomain.com I used nameservers ns1.mydomain.com, ns2.mydomain.com.

When I to ping or connect to myseconddomain.com I get info:
ping: cannot resolve myseconddomain.com: Unknown host

Should it work or I missed something? Maybe I should wait few hours? Or is there maybe a mistake in configuration? How to check it?

Best regards,
Maksymilian