Daybreak's show started yesterday morning with no audio. After the first block of no sound, they went to break and came back with ABC World News This morning. They ran a crawl at the bottom of the screen saying they had audio problems. Daybreak didn't return to the air until 6am.
Based on what I know of such things, it sounds like audio board for their news studio died. That would explain why their master control could get audio on the network, but not from their studio.