Bookstore codes, Inclusive Access codes and coupons are usually between 8-12 characters long, usually without dashes. If you ever have trouble using a code you bought from your bookstore, send an email to email@example.com with the code you were having trouble with along with a copy of the receipt for your purchase.
PLEASE NOTE: The only codes that can be entered into the coupon field at checkout are coupons, Inclusive Access codes and bookstore codes. If you're attempting to checkout and you're using a code that is 32 characters long with multiple dashes, then it is a community lookup key. A community lookup key is a code that you'd use to help you find a specific community to join. It cannot actually be applied at checkout.
Community lookup key format: XXXXXXXX-XXXX-XXXXXXXX-XXXXXXXXXXXX
If you've been invited to your community you wouldn't need to worry about using or having a community look key. After logging into your account, just go to the Join a Community page and follow the steps on the screen to join your community!