We just picked up 4 ME-500 units. They are running off an old Aviom A-Net system. 3 of the 4 work flawlessy. However, the 4th isn’t sending audio through at all. The signal light shows on the ME-500 display when a channel mic is talked into, etc, and you can hear a hiss in the headphones when you crank the master volume up. So it says that the headphone amp is connected somewhat. However, there’s never any transmitted audio to the headphones. When another unit is hooked into that same power source and ethernet they work just fine. I’ve tried the factory reset but no success. Any help is greatly appreciated. Next step is to send it back to Sweetwater for a replacement.