If you’re having trouble with installing the NOOK’s SD card, or have had trouble after installation, there are several things you can do.
First, make sure it’s the right type of card. The NOOK handles either a microSD or a microSDHC card. MicroSDHC cards are higher capacity than microSD cards. If you have another type of card, it won’t work. The NOOK can handle cards with up to 32 GB capacity.
If you have the right card type, make sure that you’ve installed it properly and that it isn’t loose. (For details about how to install an SD card, see VividView Color Touchscreen.)
Try removing the card and then reinstalling it. Before removing the card, you need to unmount it. To do that:
Press the NOOK button to bring up the Quick Nav bar.
Tap Settings→Device Info→SD Card.
Tap Unmount SD Card.
It’s now safe to remove the card. For details about how to do it, see VividView Color Touchscreen. After you remove the card, you can reinstall it as detailed in Installing an SD Card.