I've tried on two different computers (one running Catalina, one running Mojave) with different USB ports on each and differentUSB cables. Once, it was plugged into my OS Catalina Mac and a dialog box appeared asking if Garmin Express could access an external device and I said Yes and it then mounted it. I loaded an update, it ejected itself from the Mac and now it won't connect again. I tried what some folks says works by holding the lap button down when I plug it into the USB port, but that didn't help.