Please, don't publish your API_KEY as someone else could steal it from you. No data will be get if someone didi it, but someone could make your analytics data show fake events.
You are using the deprecated way of integrating with Flurry Ads. See http://flurrydev.github.io/FlurryAndroidSDK5xAPI/classcom_1_1flurry_1_1android_1_1ads_1_1FlurryAdBanner.html#a09fb49838048b0027db636ca56d8e550
From your code, it seems it is not needed any condition to show the ad, so just use FlurryAdsBanner.fetchAndDisplay.
And, as @survivor said, it takes some time to start sending you ads back. Enabling test mode would accelerate this. This can be achieved by adding your device ID on the field for the ad space. Device ID is the one which is shown on Google Settings/Ads, the one which allows advertising SDKs to see if user has opt-out.