Hi, I have heard of this issue before. It doesn't look like you will need to open your ports up on your router since it initially worked. What you will have todo is just turn the power to the amp completely off for a minute and turn it back on. There seems to be a bug in the software that forces users to do this every so often.
Also check your network cable just in case (you may also want to check for a firmware update for your amp)
Thanks Ryan. I found out the router actually was the issue. Despite the fact it works in all other regards it has seen better days.
When i directly plugged the laptop into the Receiver as a test the AirPlay functionality instantly worked.
A friend that had the same problem with a Denon receiver found that if he plugged the Airport Express into his receiver and used that as the receivers connection to the network the airplay worked. Tech support for Denon and Apple weren't able to get it working for him but this ultimately was his work around.