Unable to backup uSD card using PC?

HI all, I recently upgraded from a Pi2 to a Pi3. I was in a rush and now regret not imaging the uSD card before the swap.

I have auto-update enabled but seeing all the recent issues with Kodi17 I decided to do a backup before it arrived.

I powered down the Pi, removed the uSD card and started my usual imaging process
Insert uSD card into adapter, Insert adapter into USB port on Windows 7 PC, wait for OS to mount the adapter, run Win32DiskImager and save a copy.

After trying 2 different adapters and also trying both on a laptop running Vista - NOTING is seen on the uSD card. In Windows Explorer both OS show a removable disk (the adapter) but when I click on it to view the content it says something similar to “insert valid media”. The OS is seeing the adapter but not the uSD.

I repeated the above with a different uSD card in both adapters and bot OS could see the files and folders on the uSD card.

OSMC boots without issue so there must be files/folders on the uSD card.

I have turned updates off while I try to sort out this oddity.

No logs provided as I do not see how they would be relevant. Would you like any other info that I might have omitted?

Any help/suggestions will be more than welcome.

Try USBIT.

No luck with USBIT but possibly some information of value?

FD01: \?\usbstor#disk&ven_multiple&prod_card__reader&rev_1.00#058f63666433&0#{53f56307-b6bf-11d0-94f2-00a0c91efb8b}
FD02: Multiple Card Reader USB Device
FD04: Device ID is USBSTOR\DISK&VEN_MULTIPLE&PROD_CARD__READER&REV_1.00\058F63666433&0
FD05: Media Type is 11
FD06: Location Port_#0001.Hub_#0003
FD07: Hardware ID USB\VID_058F&PID_6366&REV_0100
FD08: Device Number is 2
FD09: FOUND!

When I clicked on Backup - Could not read from the USB device (Code:21)! The device is not ready.

I think I may have to re-image from an old backup.

Make sure you are running the imaging software as administrator.

Is the card 64GB or bigger ?

If so your SD card reader is not SDXC compliant, and will not work with cards bigger than 32GB.

No change when Admin.
Windows Disk Management console and Aomi Partition Assistant both show 14.88Gb unformatted partition.

What I find intriguing is that OSMC can boot from it but both Win machines just see an UN-formatted 14.88Gb partition.

I think I will give up. I have an older image I can re-write if needed. The main reason for wanting a backup is because transmission is running in the background and I want the current state backed up. I can back up the Transmission files manually so not a biggie.

The card is 32GB and has bean read once a month (pre upgrade) for a LONG time. Everything was fin up to the Pi2-Pi3 upgrade, I have a backup to restore so not a deal breaker for me.