I have had no problem playing my Tablo through Plex until late yesterday. Now on an iPad (too old for the Tablo app, so using the channel through Plex) the channel does not appear at all. On my Nexus 5 with Lollipop I have the channel icon, but I get the message “This directory appears to be empty.” All else I normally plan through Plex, including my son’s shared stuff, plays just fine. And the Tablo app on my phone plays too. So the issue is totally isolated to the Tablo Channel on Plex, and it was working fine until late yesterday.
My bad; LAN problem. Power cycled the router and all is well.