RN424 - can only connect using admin + password. Cannot access TimeMachine partition

Have RN424, and three Macs (Mojave on two).

Can access ReadyNAS using UN admin and a password, Can add files, etc.

In Finder, using Server and smb://<IP address>, can see and access folders - documents, music, pictures, video are shown; grayed out are admin, data, home.

Tried several ways, but the Backup > Time Machine partition (fully set up and turned ON) cannot be accessed.

Sure that I'm missing something simple...