Not sure either. I think it's AT&T issue... I can r/w from twrp but not while phone is booted. Apps like gsam root companion do not install to priv-app like they are supposed to. I have to manually do it from twrp.
Sent from my HTC One
AT&T HTC ONE (M7): rooted : Unlocked : S-on
Developer Edition AT&T Rom Here
Kangaroo Kernel Here
Sense 6 Toolbox Here