Streaming box inop

Both my streaming boxes have been working intermittently for a few months now, and now both are completely out. They power up, but no display, no sound. I was able to get them to work previously by either turning them off/on with remote or unplugging them. Just tried the factory reset, no change. I called the 1800 number and they sent me a link to further diagnose the problem, but the link is broken. I don't know where to go next.