The most common reason for this issue relates to a failed credit card authorization. Please see the topic WHY ARE THERE MULTIPLE CHARGES ON MY CREDIT CARD for reasons why credit cards can be declined and still have a pending authorization at the card issuing bank.
An additional reason can be related to a misspelled email address. If your email address is misspelled during checkout, this can result in the creation of an "almost" duplicate user account in the system. The misspelled account will be the one holding the order in this case, and you will need to use the CONTACT SUPPORT button below reach our support team for further assistance.