I mean, your screens are bare-bones simple:
Also, my immediate reaction is WHOA, why did you create so many screens? Surely there’s an easier way to do that with just one or two screens. I guess what’s done is done but… any time I find myself repeating a process more than 3 to 4 times, I stop and figure out how to create the same content dynamically.
But that doesn’t really address your question. My assumption is that you’re getting a white screen because you’re sending the PDF reader an invalid file. And the next thing I notice is that you have an app variable without an initialization or set block on the first screen of your app. I would think that would probably crash an app.
If that’s not it, then you need to separate out the steps here… for example, what happens if you assign a label’s text to that get value block but use an integer (1, 2, etc.) for the row id? Do you see the PDF url you’re expecting? If so, what is the url?