I’m having the same issue on two brand new Pro Plus.
I’ve switched cables, turned auto-sense on and off, used different input sources that are all working just fine, rebooted, reset and what ever else I could think of.
I plug the audio sources into three of my older Pro Plus’s and everything works just fine.
Sometimes if I switch the input from Optical back to Line In it will start to work but the sound is horrendous, cracks and pops with the beats, sometimes it will clear up a bit but sometimes it won’t.
Like I said, the older ones, no problem at all.
The only difference I have noticed between the new and the old are the input connections are gold on the older where the newer are shiny black. I’m doubtful that makes a difference though.
The same problem is only with the two new ones I just got. It’s extremely frustrating!