No help at all

So the app requests a flight number, but its ua####. The app doesnt show me letters only numbers.
I tried with out ua and app tells me no flights. A better explanation would help me. Then I try the airport and time and it again says no flights. Im trying to find out when my brother-in-laws plan will land.
Dont think this app was any help to me at all.
If I tell it flight number or airport and time why would it says no flights ?

Lefty malkowitz about United Airlines