I decided to bite on this and ran into the same message about contacting customer service even though I've never had a magazine subscription from B&N ever. Seems the problem is the free trial period, this is what support finally told me:
I was able to see that the order is pending, though the payment is okay. This is still on trial period, so please disregard the message as this will go through eventually. We apologize for the inconvenience.
So apparently their system interprets the pending credit card charge (due to the free trial period) as a problem to notify you of. That's... pretty darn moronic.
But at least the order is okay.
Also, because this confused me and will probably confuse others, you'll only get the current issue of Asimov's immediately, the rest take a couple of days. The E-mail you get explains it like this:
Your first issue of Analog Science Fiction and Fact will be automatically delivered to your NOOK library in approximately two days along with the 12 prior issues (24 in total) of both Asimov's Science Fiction & Analog Science Fiction and Fact.