A remote system shows up as "Offline" in both the All Devices and Recent Connections pages
However, the device IS online. If I click "Show Details" from the 3-dots menu, it displays as being online (green check), and I CAN connect to it from that panel.
In case it's material, the remote is currently on the same LAN as the system initiating the connections (but won't be long term).
The only way I've found to restore the expected behavior is to completely exit and restart TeamViewer on the initiating (local) system.