Intermittent USB access

I’m new to the Beagle. Plugging in the USB cord sometimes gives me access, sometimes does not. I thought it was the cable, then the USB hub, but it has worked and not worked on every combination. The rule seems to be that, if no volume appears on the Mac desktop, I have no access through USB, even though the blue lights are blinking away.

But, I can get in on ethernet.

Any thoughts? A bad jack or USB port on the BBB?