If you redeemed your code on the website, but the app is still asking you to pay, you are likely logged in with a different account.
Here is how to fix it:
Check the exact email address you used when redeeming your code on the website.
Log out of the URUNN app (Profile → Settings → Log Out).
Log back in using the same email and password you used on the website.
Tip: If you used "Sign in with Apple" or Google, make sure you use the exact same button on both the website and the app!