I really wish this was an actual answer instead of just another comment.... I'm having the same issue and have also started a support ticket. My GR light and no audio in/out occurs with and without the computer connected so that eliminates the problem being the computer or the firewire cable. My mixer has not been moved or disconnected in a few months and has worked perfectly on a daily basis. I have attempted all possible fixes... Toggled the Firewire Link ID 0/1, reset to factory settings, current version of Universal Control, etc.
The old forum has a long list of possible solutions dating back 5-6 years but none seem to work. Like many of us on here, I am a big supporter of Presonus but this known issue and the fact that I have to pay them to fix the problem is enough to steer me away from their products in the future.