The specified domain either does not exist or could not be contacted

I have yet another newbie question on Active Directory.

I was provided with an IP address of a Domain Controller and credentials administrator@itdrde.local.

I was able to connect to AD with Active Directory Users & Computers tool from my Windows 10 machine that is not in the domain (see the link for details).

But while trying to add a user I got the following error:

Does it mean that something is wrong with DNS, for example?

At least I can ping itdrde.local from the command line.

EDIT1

I was able to a computer:

but not user. What is the difference?