I apologise, I’m not sure how I missed this. It seems some source devices don’t turn their optical signal off when put into standby, so the optical output is always transmitting something. Because of this, there would be no change to trigger LS50WII to come out of standby, hence why the unplugging/plugging back in triggers it - there is a change from no signal to signal.
I see that some of the Hifiberry digital products have coaxial digital output - if you happen to have a suitable cable, you could give that a try - if it doesn’t send out a constant ‘active’ signal, then wake-up should work fine. Plus you would be getting a 192/24 input this way, also.