Dear member of SanDisk Community, welcome.
[ Does anyone know if there is a way to recover the stuff on the SD cards? ]
1- Test your SD card, in a laptop directly to its port-card, (not USB card-reader).
2- If still bad: in Start / My PC, on the card icon right-click, and then click in Properties / Tools / Error Checking and Repair.
3- If still bad: try formatting with the tool (portable app, free): USB Flash SD Formatter 4.00
Then, remove and re-plug the device.
4- If the card is recognized by the Operating System, the Data Recovery is simple and free.
Do not do it for Internet, understands me?
Download to your laptop, this tool (portable app, totally free), configured to use to “one touch”: Recuva 1.51
5- If there is no joy, then please, do not grieve more friend, return it.
[ I also can’t remember when I bought it (and I’m certain I don’t have the receipt). ]
You might have a pleasant surprise, if can contact SanDisk Technical Support
who will replace the device, if it’s authentic and is within warranty: Link
Regards, Alfred. (Google translated)