If you can't see ANY nands then they're likely just faulty in some way (corrupt dumps, dodgy char in name, disk/filesystem not compatible in some way etc. etc.).
Assuming you can see at least one of them ok then I'd just make a copy of it as usb:/nands/nand3, say, and see if this can also be seen to make sure you've not discovered some bug whereby multpile nands aren't being detected...
Assuming you can see at least one of them ok then I'd just make a copy of it as usb:/nands/nand3, say, and see if this can also be seen to make sure you've not discovered some bug whereby multpile nands aren't being detected...