How do I revive my dead 2010 Audi A8L?

key sticks in ignition and totally dead. I know how to release the key with the pinhole. I have replaced the battery in the key fob, but there is no recognition of a key.

i know that a dead car battery will cause those symptoms, but I just had the battery replaced. I am wondering if this might be the issue. When I had the battery replaced - local big box store -  I was told that they would reset the code, but when I picked it up, they told me that they weren't authorized to do any code related things and that I had been given incorrect info. So, I took it anyway and haven't gotten it reset. It's been about a month. I remember getting a low battery warning since then and I'm wondering if my car thinks it has the old battery and thinks it just HAS to be dead by now and acts as if it IS dead?
Will a generic code reader work at this point (my brother has one), or do I have to have someone with an Audi coder come to my location to do it? If I recall, it's code #61. Or is this even an issue?
Any other things to check/do that might revive my dead A8L?