Another thing to try is a different power adapter. Tablo sells them for $12, and some folks have bought a higher amperage one from Amazon (link to thread).
Though you may want to contact Tablo support to see if they have other ideas.
Although you tried the 30/30/30 reset, did you try the Tablo documented reset procedure? Even though your Tablo doesn’t appear to boot, maybe there is some helpful info in the article.