My device: Galaxy Tab A 9.7 (SM-P550) 6.0.1
So installed TWRP via Odin -success Then I flashed supersu via twrp -success
Then I tried to flash xposed via twrp -fail
What I think happened was that it was the wrong SDK. I was supposed to install SDK 23 but I installed 21. So then what happened is that it failed and I tried to reboot back into the system and now all it does is reboot back into the TWRP menu and I can get into the lockscreen. So I tried formatting the data, factory resetting, wiping Dalvik/ART Cache and the Cache and tried repairing the file system and still can't boot into the lockscreen.