Helll
Hello , I been buy the Traktor dj app and now is not work and when i ask them is been tell me to ask Apple
iPhone 8, iOS 13
Unfortunately I'm not sure how Apple can deal with this because it's the fault of the developers of the app which reasons as to why the app is not working. You could potentially wait until an update rolls out for the app in hopes of it being fixed or you can request a refund of your $9.99 on the app.
Support for the developers: https://support.native-instruments.com/hc/en-us
Reporting a problem/refundinhttps://support.apple.com/en-gb/HT204084