Hey folks - We finally have some insight to share on this.
Most mobile carriers offer support for both the IPv4 and IPv6 standards. Up until recently, T-Mobile also supported both (which is called 'dual-stack').
Tablo Connect's mechanisms work on IPv4 and do not yet support IPv6. Adding support is possible, but will require some fancy footwork on our side in terms of DNS translations.
Now that we know how to tackle this problem, we'll be able to take a closer look at it in the New Year. Beyond that, I don't have an ETA on when a fix might be coming. (UPDATE March 14, 2018 - We do have a potential fix in the works. Stay tuned!)
Some folks using other apps on the T-Mobile network on Android phones have reported an improvement when they've changed something called their APN setting to allow traffic from both IPv4 and IPv6.
This setting is different on every Android phone so unfortunately it's not easy for us to provide a how-to and since we're located in Canada, we can't really give it a try internally. This setting is not available on iPhones.
In the meantime, streaming TV via Tablo Connect on WiFi networks vs. LTE should continue to work.