Tablet won't respond to any buttons and Knox commands don't work.

There's a button combination that will put it "dev" mode and will allow you to reset it that way. It's the power button + the volume up button + the home button on the screen. Press and hold those together with the tablet turned off and unplugged from power. You can release when you see the Samsung logo. Once the new menu appears, use the volume up and down buttons to highlight "Wipe Data/Factory Reset" then use the power button to select. It'll ask you to confirm your choice and use the buttons to highlight and select "Yes" When that command runs it will take you back to the main Dev screen and there you'll select "Reboot System Now". After that it'll reset the tablet and boot up to the welcome screen.