Kindle connecting to wifi, but not syncing with Amazon cloud

Question

I have a new kindle (I've had several and have had no trouble before) and it connects to my internet no problem. However, when I buy a new book, it doesn't always show up in the cloud or on the device. Sometimes it shows up immediately, sometimes it's hours later. AT&T says it's an Amazon problem. Amazon says it's an AT&T problem and neither will help me.

kelam715 · Answer

Also, I've tried everything to fix this...restarting my router, forgetting the network on the device, restarting the device, etc, etc.

It has to be some kind of setting in my router configuration, but I don't know how to fix it and customer service wants to send me to a third party for $49. I'm very frustrated.