LDS Library won't stream audio over carrier (T-mobile) network

I am unable to stream audio within my LDS library app when I am on my T-mobile 4g LTE. Everything streams fine when I am on wifi, though. It's the same story when I try and stream directly from lds.org.
Other family members are able to stream on their devices (Android). My device is an iPhone 5s.
It has worked in the past but doesn't work any longer.

Any ideas why this might be happening?

Try going into the SETTINGS app on the iPhone, then click on CELLULAR, then scroll down to the section where is says USE CELLULAR DATA FOR: and find the LIBRARY app, and make sure it is turned on.