Meanwhile the list you see is the one saved on this PC, as it was when the server last confirmed it. A short interruption, for example when the PC wakes up, does not show the message.
The message says since when SyncNow can't reach the server and, when it differs, the time the list was last confirmed. As soon as the server answers again, SyncNow reloads the full list and the message disappears by itself; its close button hides it until the situation changes.
While the list is not confirmed, a project in it may no longer be available to you, and if the server really cannot be reached, agents cannot open projects or work on files either. If the message stays, look at the Online or Offline dot at the bottom right to see why: What do Online, Offline and Not connected to SyncNow mean at the bottom of the window?.