Windows Admin Center 2410: cannot add computers

After a fresh installation of Windows Admin Center 2410, I cannot add any servers, clusters, PCs etc. WAC gives me "You can add this computer to your list of connections, but we can't confirm it's available" when I enter a computer name (either of FQDN or computer name alone).

When I change to the Search Active Directory tab, I get: "We can’t search Active Directory because the Windows Admin Center computer isn’t joined to an Active Directory domain. It’s also possible that your account doesn’t have permission to read from Active Directory.​"

The account I use is a domain admin, and the server running WAC is definitely joined to the AD DS.

The server had the previous version of WAC installed where everything worked. Now, with the new version, that's no longer the case...