Leaderboard advertisement

I am trying to get the adsense code to be shown on the leaderboard area or the header sidebar on desktop. I have selected the widget to display the leaderboard advertisement, but the advertisement does not shown up there, whereas all other widgets including Mrec advertisement on sidebar are working properly. However, when I select an image from the header sidebar, it shows perfectly on the leaderboard space.

What’s the issue?

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