In the device manager, if looking at cameras tab (which is default tab upon logging in) the screen will show 'System Unavailable.... Your GS2 processor is busy applying updates. This process may take several minutes. Once updates are complete, you'll be returned to the admin utility.". and this will loop indefinitely.
This can result because we've lost connection with the cameras, to gain access to the device manager click out of the 'Cameras' tab and the prompt should stop appearing. This will be fixed post 19.3.