Open Activity Monitor and make sure that Box (the Box Drive app) is not running. If it is, highlight it and click the quit button in the top left corner (looks like a stop sign with an "X" in it). Select "Force Quit".
Open Activity Monitor and make sure that Box (the Box Drive app) is not running. If it is, highlight it and click the quit button in the top left corner (looks like a stop sign with an "X" in it). Select "Force Quit".