I followed Google's AdMob implementation guides for mediation iAd/AdMob. I created AdMob account with Google and iAd network account with Apple. My code for iAd/AdMob mediation works apparently. In the simulator when iAd loads first and when it fails, AdMob banner loads. However, on the device, iAd loads and when it fails AdMob never loads.
I don't understand what to do differently because i've never had an issue with something working on simulator but not device. I'm receiving no errors from Xcode.
What can be some of the reasons why AdMob banner would work on the simulator but not on device?