I have the same problem with PostNL. A couple of weeks ago the app was running just fine.
Now when filling in my Tracking ID, the status will always be:
"No status information available yet"
When I use "Show in browser" The PostNL gives me an error in Dutch.
"Het land is niet ingevuld of gevonden." Which means: "The country isn't filled in or found."
When i press "Find my parcel" on the website, it works just fine.
Hopefully you could take a look at it.