Hi @aviad dror ,
According to your description, I created a simple demo to reproduce this issue, and I found that when you add the opened website to Edge IE mode sitelist, you can get the returned handler from
window.open method. But if the page opened by window.open method displayed in Edge(not in IE mode), then you will get null from this method.
Something like this:
As you can see, I use
console.log() to display the handle object in the console, not null. So I think you can try to check the configuration I mentioned above.
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