This Krell product does not support convenience switching (automatic switching of the input at the start of playback).
It’s necessary to switch the source to “network” manually using the IR remote or front panel. If you try to start playback from Roon while any other source is selected, that error message is displayed.
We did add the artwork in a recent release, but there were no other changes on our side that could have caused this problem–I suspect that the difference between the two times that you tested is that in the second test “network” was selected.