Not sure if this is a bug or not but I actually got stuck on this the other day and couldnt figure out why I had no audio. I somehow had it muted in mix but didnt know it was muted because the mute button on the left with my instrument wasnt lit up. See image. Isnt a big issue when you know about it but to new users (like myself) is a weird issue that might aswell be fixed.
Also a thing to note, for most of the time I dont think I had mix open, so I couldnt see it was muted. Theres still the red m in the bottom left but thats out of the way. But its just weird that 2 of the 3 m's turn red but one doesnt.