NOTE: This is for an iOS 15 app

I finally found the solution. I believe I was calling it too early, as the requestIDFA function was called within the application("didFinishLaunchingWithOptions" ) in app delegate. If I moved the above logic to applicationDidBecomeActive function, still within the app delegate, it works. Hope this helps anyone who fell down this rabbit hole. It is weird that I previously got the popup to display through the initial approach in the beginning of development.