The check would be for the sales period ending two months before. That's the only thing I could think you might be overlooking. Does it match up with a previous month's report? If not, I'd contact Support ASAP. Good luck!
P.S. If you live in a different country from the US, I think they deduct 30% for tax withholding if you hadn't filed some kind of paperwork exempting yourself. I'm not sure about that though.