The following reasons are common causes of ads not displaying in newly Enhanced apps:
The most likely cause of ads failing to display is that the network has nothing available to be displayed for your particular location at that specific time. Unfortunately there is no way to guarantee fill from any particular ad network, but you can try the following to help avoid it:
Try with a test code. Many networks will offer 'test' ad codes which you can enter into Enhance. These test codes will generally show test 'implementation successful' ads which will have 100% fill, but will not generate any revenue. This is useful to check that the problem really is lack of fill.
Try using a VPN. If the ad network that you are trying to use has fill in specific geographic regions which don't match your current location, using a VPN for testing can help, for example a VPN based in the US could be used to test a network which only provides advertising within the US.
Since Enhance inserts a lot of code from ad network SDKs into your app, if you leave any code from previous ad network implementations in your app you may encounter conflicts.
If you're encountering issues, be sure to strip out any existing ad network implementation code and library files/dependencies before running your app through Enhance.
Even though our implementation is quite simple, in some cases the methods such as showInterstitialAd may not be called at the correct or expected times. A good way to troubleshoot implementation issues is to test your app before running it through Enhance - a dialog will be displayed to inform you that you've implemented things correctly.
After Enhancing, you can check device logs to see when various Enhance methods are being called.