If your SD card is not recognised there are possibilities:
1. The manual - I'l give the link later in case yours is mislaid - only mentions "Micro SD" up to 32Gb. Sometimes these cards can be the SDHC category and these are not always accepted in devices designed for SD only. They look identical so make sure yours doesn't say SDHC.
2. The file format on the card can be significant. It needs to be a format compatible with the phone. If you have no other data on the card, it might be easiest to see if the phone will format it.
3. Of course it might be a faulty card - can you test it elsewhere?
The link for the manual mentioned above is here:
Proscan Media Tablets eBooks ReadersInstructions Manuals Quick Start...
Its about 15th down the list and will download direct to your computer.
With regard to downloading from nand to SD card, is this essential? If you have a micro USB to normal USB, then you should be able to use a computer to take data from the nand. The nand would show up as a drive in "My Computer".
Hope this is helpful, if so would you please register that with Fixya