Just an observation. I have had trouble with up loading sketches to various boards using the IDE for the past week. The error message indicated that the USB port on the Mac was 'busy'. A similar message appeared when just trying to open the serial monitor. I tried every published fix in the forum with no success. My Mac is enrolled in the Apple Beta program and was running a beta version of Catalina which was frequently auto updated. When I resigned from the beta program and installed the latest production version of Catalina my problems disappeared.