I am using Plex on a Seagate NAS Personal Cloud device. Up until now I could not play any video using the Plex Tablo Channel for some reason.
I installed the latest update yesterday and the Tablo Channel is at least playing back video where i could not do this before.
The Tablo channel is really long in the tooth but at least now I can play directly from my Apple TV 4 using the Plex Tablo Channel until we can get started with the Tablo betas 
If you have a Plex update for your praticular server it might be good to update it as it could solve some issues for you.
All the best,
Simeon