Multi player Mine craft doesn't work on Kindle Fire. It just says "scanning for wifi games"
You have to have someone playing near you to play in their world. Then you select them. You cant play on line. Only Minecraft pc edition does.
It could be that the Minecraft game settings are not linked to the Kindle Fire. Also, try checking if your WiFi settings have been correctly installed. If you still have the same issue, you should have a game expert check it out for you.
Try using the same file on a device that has better wifi, or go to a local wifi like a fast food place. Trust me, you are probably not the only one