The versions later than Android JB 4.2.2 introduce public key authentication policy when connecting to PC host via ADB. This feature keeps the ADB offline until the device and PC pass authentication.

With security ADB enabled, Android SDK Platform-tools in PC host side higher than revision 16.0.2 is needed to make a valid ADB connection. Otherwise, the PC cannot connect the device over ADB (the status is always offline).

With the latest Platform tools, the device displays a dialog to remind you to allow ADB to connect or not when connecting the device with the PC through ADB.

Then, you need to select “OK” to allow the PC to connect your devices. If you select “Cancel”, the ADB connection is rejected. For running the CTS, you need to select “Always allow from this computer“. Otherwise, the device still needs your confirmation in each reboot. To disable it,

delete this line or comment it as follows:

#setprop 1