Device suddenly unauthorized for adb
You can try the following:


adb kill-server followed by adb start-server
(on device) Settings -> Developer Options -> USB Debugging -- switch off and on
[Windows] Make sure you have the proper driver (your best bet is Universal Adb Driver by Koushik Dutta -- will handle any device)
[Windows] Try turning off all fancy on-the-fly anti-malware scanners/firewalls
[Linux] Make sure you have the proper UDEV rule in /etc/udev/rules.d/51-android.rules (again, universal solution: https://github.com/snowdream/51-android)
[Linux] Try using adb as root
Restart your phone 
Replug cable, try different cable, different port, remove any extender cables


I hope somthing works for you :)