Books Project Sample - Overlay not showing

Hi, 

I am getting totally same issue but in Android.

https://developer.vuforia.com/forum/ios/books-sample-project-confusing-issue

The project builds and runs fine, and all the trackers work great. I modify the keys as well as the download URL for the JSON content.

I create my own cloud target database. I create a tracker and upload a metadata text file that contains the JSON file name.

Then, I run the project again.

Now, it find the target just fine. It downloads the metadata just fine. It even downloads the JSON file just fine. But here's where things get weird:

While tracking the target, I never see the overlay (the one with the book details). If I move my device away from the target, the overlay appears on my device (just as it should according to the Book demo). But if I then go back to tracking, I still don't see the overlay!

Note : I suspect this was related to  width of image target - I have provided 25 , 50 , 100 , 200 , 300 in width sizes but the result is same. Please help me out . I m using latest vuforia sdk.