I’ve saw this issue some time ago on one of my previous Mavic Pros.
For whatever reason, my Windows desktop PC simply could not see the MP via the adb shell (yet connected fine via DJI Assistant). I don’t know if it was a firewall setting or what, but I gave up trying after a while and used adb on the Mac instead, which worked first time 
Are you running ADB as Administrator on Windows?
Got a Mac/Linux pc you can use instead?
And if you fly with DJI GO or Pilot, don’t forget to remove NFZ from your apps too 