We've heard from a few folks that their $100 credit for their Lumia 900 has not been applied to their AT&T account and now we may have an answer. While rare, there seems to be a reason that WinSource has stumbled upon.
In essence, if you bought the phone at full price and didn't use an upgrade (or new activation) then the credit won't be applied to your account. The reason being Nokia doesn't "know" that you bought and activated the phone on your account. While odd it sort of makes sense because for all they know, you bought the phone and sold it on eBay or sent it overseas.
The problem seems to be easily resolved by simply calling AT&T and double checking. In this instance AT&T verified the phone was on the account and applied the $100 credit which was a nice gesture.
The $100 credit was offered by Nokia (via AT&T) to those who purchased their Lumia 900s before April 21st due to a connectivity issues with a small number of devices.
Anyone else having problems getting the credit applied to their account?