new SanDisk SD cards do not work - what's the problem??

I just bought 4 new SanDisk 64 GB SD XC cards from Best Buy, for use mainly in my Pentax K-1 Mark II DSLR Camera. When I plugged the just-out-of-the-package cards into an SD card reader connected to my Windows 10 computer, two of them pretty much seemed not to work. The other two cards behave as expected/normal - I just plug them in and I can do whatever I normally do to a disk drive (write to it or give it/change a volume name).

I keep getting a “card is write protected” error message if I try to format the card, change the volume name in Windows Explorer, or try to write a file to the card. And, YES, I know about the little slide write-protect switch on the card. That switch is in the correct position for the card to be written to. I’ve slid it back and forth several times, and nothing changes in the error message.

This is the situation on both of my Windows 10 computers - my main desktop PC as well as my MicroSoft Surface laptop. (I have yet to try the old Windows XP machine.)

On a whim, I figured what the heck - just stick it in a camera and see it it works. One of the questionable cards went into the camera closest at hand, my K-3 III, where I formatted it in the camera, but did not actually try to take a picture. However, it seemed to pick up the volume name of the previous card that was used in the camera. But, I’m not sure that the volume name was not erroneously given to it by my PC, where I’ve often seen the name of a previously ejected card/drive be applied for the same drive letter name when a different drive is plugged in. (At this point, after so much messing around, I do not remember if that card behaved normally in the computer after the K-3 III format. I think it was at least partially usable.)

A search of the web indicates that there can be software write protection for a card, so I went through a procedure using “diskpart” in a command window to clear that write protection. To no avail! There appear to be other options as well, doing things like editing the Registry - but it seem to me that would only fix things on a particular computer, so I haven’t tried them (yet).

Finally, I figured I had nothing to lose by putting the cards in my K-1 and trying to take some pictures. Amazingly, that worked for ALL the cards - whether or not they had been formatted in camera the K-3 III or on the computer, or NOT FORMATTED AT ALL. I just put the cards one by one into the camera and took a few frames (DNG+jpg), and the all recorded the expected image. For the two questionable cards, I could readily read out the image files into my desktop, but I still can’t use the computer to do anything else to those cards - can’t format, write a file, or change the volume name!


Has anybody experienced a similar problem with brand-new, name brand cards (I hope Best Buy has not received some bootleg cards).

If so, what was the cure, if any? Thanks for any help!

I have a strong suspicion these are going back to Best Buy on Tuesday next week!

Hi @mariagreen
Have you opened a Support Case? If not opened, for more information, please contact the SD Technical Support team for best assistance and troubleshooting: