Android Studio (adb) stopped to see my device (Mac) -

i have nexus 7 tablet, , android studio, , able see tablet yesterday or 2 days before, since yesterday or today when connect device, dont see in devices list when want run application.

i tried quit android studio, tried kill adb (ps -e | grep adb kill -9 pid_adb) , seems killing of adb had effect, because window when 1 selects deployment target displaying message "initializing adb", still dont see device. tried turn off , turn on tablet, nothing worked.

i tried disconnect , reconnect usb cable, tried restart mac.

i tried turn off , turn on developer debugging in tablet settings.

this tablet runs android 5.1.1. have 2 more devices (android 4.4 , android 6) , both visible.

i using mac (from experience mac better detect usb devices windows btw).

what problem in tablet's notifications see there pending system update ready - android 5.1.1 - "downloaded , verified, click restart , install" strange because in system info see 5.1.1. if pending installation block usb debugging dont know.

does know why stopped see device, problem?

thx

probably obvious did try:

restarting adb using server commands:

adb kill-server adb start-server 

use known usb cable ie. 1 works other devices worn cable can stop working.

make sure when turn developer options on (on device) turn on usb debugging. usb debugging icon should persistent notification on phone.