I decided to run some tests on my work ATT wifi it wasn't loading but when i turned off wifi and used my Verizon 4g it loaded.
So i went back to wifi because i am not on an unlimited verizon plan to be downloading all these files, and it works.
I was able to recreate it on a tablet so i believe only the inital sync of the app is needed on a network not on ATT after that you can use the app normally.
Give it a try and see how it does work.
1st open the app on a non ATT network then switch over to the ATT wifi you're using.