Is the red light on the adapter illuminated? Have you tried connecting it to all 3 USB ports to see if it lights up, and have you tried connecting it to the other Hopper?
Red light was on when tech first connected then went out. He indicated it would come back on when I went into my account and linked to Hopper. No option to link. Looks like it links automaticly if all is ok. I did try other USB and second Hopper. No red light, no indication that USB device attached. Almost looks like Sling crapped out at time of conversion.
I hate to say it, but that was the symptom when my Sling Adapter croaked. No red LED, no matter which USB port I plugged it into on my 722k. The replacement from Dish fired right up when it was connected.
I'd let it cool down if it's been plugged in for awhile and see if that makes any difference. Also, I'd unplug any other USB devices from your Hopper to see if that makes a difference.