CR 10 Mini - isn't found by Octoprint on RP3+


What is the problem?
I've installed octoprint using the octopi distro on my raspberry pi 3+. The distro seems to be working fine (I can log in remotely etc), but when I plug into the printer, it doesn't find the printer. I've just plugged in a USB type b lead into one of the raspberry pi usb ports. Wondering if i'm missing anything obvious?

What did you already try to solve it?
Tried turning it on and off obviously! Swapped the cable around the ports.

Additional information about your setup (OctoPrint version, OctoPi version, printer, firmware, octoprint.log, serial.log or output on terminal tab, ...)

Latest version of octopi distribution (downloaded yesterday) - printer is a CR-10 Mini, with stock firmware.

Any help would be much appreciated!