Why I'm not seeing ads?

I've made a UWP app, test values are working great but when I download from the store, ads are not showing up (and I've replaced test values with ad unit from dashboard).

<Advt:AdControl ApplicationId="*********"
                                                    AdUnitId="******"
                                                    HorizontalAlignment="Stretch"
                                                    VerticalAlignment="Top"
                                                    Height="120"
                                                    Grid.Row="2"/>

Solution

There are two reasons could cause the issue that you have mentioned.

The real ID(values with ad unit from dashboard) starts serving in 24h after your app has been published successfully.
Another reason can be that you have not set the right size for the ad control, for more please refer to Supported banner ad sizes.