Andrew,

I trust that you have tried other USB ports, directly into the laptop, not a USB hub.  Let's have you walk through a sequence that will help define the source of your issue.

Sometimes, a USB port/hub can have a 'sticky' bit and fail to work.  Here is a series to try.

1)  Power off both the scanner and shutdown, then power off the laptop AND power off AND then unplug the power sources, INCLUDING the battery (both devices and any other connections on the laptop).

2)  Have a cuppa (well, wait at least 2 minutes), then replace the power source(s) (batteries), power both on and see if the scanner is now recognized.

2a) You can see if the SD card is still not seen in the scanner at this time.  If not;

3)  Check to see if the scanner is recognized (device manager) in another system, preferably in BULK DATA mode (so it looks like a thumb drive to the OS). 

At this point:

If the scanner is recognized on another system and not your laptop, it's the laptop causing the issue (likely a munged up driver).

If the scanner still isn't seen by any computer (and still can't read the SD card), it's the scanner; the USB has failed.  That the scanner is apparently not seeing the SD card, this supports that theory, it's likely sharing the chip set.

Good luck!

Regards,
Rick NK7I