device not seen via USB

Might help if you tell us what device? Also ensure you're using Garmin cables, and are connecting directly to a usb port, not via a hub.

It's a Nuvi 2797LM. Used Garmin cable on all computers before trying the kindle cable. Connected directly to
USB 3 and USB1 NOT via any hubs. Gone through all of the faq's etc.
None of the macs can see the device.

Try the tips is this FAQ https://support.garmin.com/support/searchSupport/case.faces?caseId={6fa1cca0-486e-11dd-6d60-000000000000} and in particular the link to here http://support.garmin.com/support/searchSupport/case.faces?caseId={77a3a150-4ad7-11de-f35c-000000000000} about System Profiler

Note that if still no joy the advice is to contact Product Support.

Try the tips is this FAQ https://support.garmin.com/support/searchSupport/case.faces?caseId={6fa1cca0-486e-11dd-6d60-000000000000} and in particular the link to here http://support.garmin.com/support/searchSupport/case.faces?caseId={77a3a150-4ad7-11de-f35c-000000000000} about System Profiler

Note that if still no joy the advice is to contact Product Support.

This was the first port of call. Is there any way to re-install a driver for this device?
I can't see how the cable can be any different from
a Kindle cable, unless garmin have made a weird arse crossover cable to prevent people using anything other than their proprietary one.
But that would be a dumb thing to do.
Some sort of "wipe this device and start again" installer would probably be handy, as it may be a corrupt software issue. However it's a
bit tricky when the computer won't even recognise it's got something plugged into it.

Cables are different, see here

https://support.garmin.com/support/searchSupport/case.faces?caseId={e3ba99d0-fccb-11dc-ec92-000000000000}

HillsWombat

Make sure that you are using a micro USB cable plugged into the bottom of the device and not a mini USB cable plugged into the mount on the back. There are no special drivers for the device as it connects as a mass storage drive. If you are still having trouble, it may help to know what you see on the screen when you plug it into your Mac.

Jason

Thanks Jason,

I am plugging the garmin supplied cable into the right connector. I don't think it'll fit in the mounting block which seems to be more of
a standard mini usb.
On screen when I plug it in is a graphic of the device with a computer cable plugged into it. I know that's what I should be seeing,
so I'm really leaning towards the problem being the Garmin supplied cable that came in the box.