Banners inside Nav tag

I'm trying to put a banner using google ads inside my webapp, in a nav menu but I'm not able to show it. What I only can see is an iframe with an empty body inside it (which means that google ads did his work correctly, but for any reason, the content cannot be visualized).

Does anyone knows if it's possible to put a banner inside a nav menu? I've tried to put other banners in my webapp and all of them are shown correctly.

Thank you,