From regular sale to short sale? Now what?

Here is my situation. Our offer was accepted by the seller in Sept. We had our inspections, had our appraisal which came in at the price we agreed to pay, finally our FHA loan was approved, but the underwriter ordered another home appraisal to verify the home's value. That appraisal was finally settled at $30k less than the price. Consequently, this changed the parameters of the sale to a short sale, and now their lender must approve. I understand the FHA HUD appraisal is tied to the house for 6 months, so we are being told the bank should no doubt accept, we are in escrow ready to close. What chance is there the bank will drag it's feet or reject the offer altogether? Why would they? It has been a week and the seller's agent is trying to get a decision from the bank? Do we hold off, we do have an appraisal contingency. Any advice is helpful, thank you!!!