BTW, you may need to make sure your card reader is SDXC compatible, too (as there are some protocol differences between SDHC cards and SDXC cards, where support for newer UHS 3.x or higher versions is needed for proper SDXC card support).
Also, what Operating System are you using now?
Keep in mind that SDXC cards use an exFAT (versus FAT32) file system by default (a camera with SDXC support is going format them as exFAT, which is the way they come from the card manufacturer). Were both of the cameras you used with that card with SDXC compatible? If not, that may have caused some of your issues.
If you're using Win 7 (or Win 8.x) with all patches applied, exFAT support should already be there.
But, if you're using XP, you'll need to download some drivers for it. With other Operating System, support varies (but, exFAT drivers are available for most operating systems, including linux, with a number of linux distros already including drivers for exFAT). Those file systems are similar in some respects, but different enough to cause major issues if you're trying to use a FAT32 (or older "vFAT") driver with media using an exFAT file system.
IOW, if you're not using an SDXC compatible card reader (and some models have firmware upgrades available from their support pages for adding SDXC compatibility,) and an Operating System with drivers that support exFAT, you're going to have problems.
Anyway, for starters, you need to be using an SDXC compatible card reader with recovery utilities like Photorec, not a USB connected camera. Let us know more about your setup for starters (OS, card reader type, etc.) and if you can't get the photos from it using available Photorec options, we can try to make a disk image copy of the card and work with it that way (although using that type of approach really shouldn't be necessary if you're using an SDXC compatible card reader with the "whole disk" option in Photorec, unless the partition table is corrupted or the card has physical errors).
But, you'll still need a card reader that works with SDXC cards, even if we use utilities that make a block by block copy of it using linux utilities (writing to a disk image file that we can use other utilities against, while ignoring the partition table and underlying file system entirely).