I have my Firestudio 26 X 26 mai n output connected to powered monitors and they work fine. However, I also have general outputs 7/8 routed to a power amplifier/PA and 5/6 routed to a headphone amplifier and they will not work. In fact, over the years, they seem to work intermittently but now they will not work. My Firestudio lights on the front panel as well as my DAW meters show a signal coming through but they will not work. As a cross check, when I plug my main output into my PA or headphone it works fine. Any help?