Need to delete data for an app. Tried several ways with no success.

When you delete an app from your iPhone, it's gone. What remains of residual data in the System will over time be overwritten by other data. The last thing you can do after deleting an app is to remove its data from iCloud - this does NOT happen automatically when an app is deleted because if you download the app again, you have not lost data.

You can delete data from the app in iCloud here:

Settings > Apple ID > iCloud > Manage Storage

Find the app in the list. If you can't find the app, it hasn't saved anything in iCloud. The only thing you can do now is turn off your iPhone and turn it on again. Upon a restart, iOS also cleans up a bit.

To delete app data first delete the app (and make sure it’s really gone, and not just removed from the Home screen). Then restart your phone, because until the phone is restarted the app’s data is still on the phone, and if you reinstall the app before restarting the app will find it.

The other issue is the app data may not be on your phone; it may sync to or back up to the app providers server. The only way to delete this data is to delete your account with the app provider.