Samsung Galaxy Tab 4 crashed. NEED HELP ASAP!

[AC Question]

I rooted the tablet. Then installed Xposed installer and Xtether to get a WiFi hotspot on it. When I rebooted it I got the "System software not authorized by AT&T has been found on your tablet. Please turn off your tablet and go to the nearest AT&T store for help."
I need help ASAP!!

 

[Rukbat]

Go to XDA Forums and see if you can get a ROM for that tab. Then go to [Samsung] How to flash Stock ROM via ODIN for instructions.