I had similar issues but resolved it.. On your nook friends app select the + sign and then use your friends B&N account email address. I think the manual says you can use any email address, but this never worked for me or my friends. Requests went through and my friends show in app now.
Same thing is going on with my Nook Color too. I add friends and send requests, but no one shows in my friends list. This is sad that they can't get this to work better. Of all the marketing they do, they should put some time and money into the developers to make this run better to give users what they've been promised! I'm very frustrated with this gap in functionality!