Changed the region where exactly?
The Apps are tied to the app Store's region which in turn is tied to the Apple Account's region. Is that what you changed?
The device's local region is not relevant. Also, you need to make sure the app is downloaded from the store again and not from the purchase history of the Apple account.
click here ➜ Change your Apple Account country or region - Apple Support
Do note, this change requires cancellation and expiry of all active subscriptions, usage of all available account balance and no pending charges, pre-orders or season passes. You will also need to provide a payment method from the new region to verify the change.