FYI only, we recently installed "LAC Falcon" into most of PCs and servers as our Japan HQ requests. I'm not sure whether this is related to the issue that we can't view the RU Hosts. (But it was almost no problem last week.) LAC Falcon: https://www.lac.co.jp/english/service/operation/lacfalcon.html Thank you.
Just for your information; all PC were showed as Offline, but, when I tried to login a targeted PC, it prompted the password and actually I could login it. Then the attempted PC remains Online. Once I closed the Viewer UI and reopened, all PC were showed as Offline again. Thank you.