iOS NotificationServiceExtension is not working

I have enabled NotificationServiceExtension in my app. And done the following

1. Added .apppex under Frameworks, Libraries and Embedded contents
2. Confirmed both deployment target version is 12.0
3. Sending mutable-content": 1 in my apns notification payload

4. Following is my NotificationService's didReceiveNotificationRequest method

   - (void)didReceiveNotificationRequest:(UNNotificationRequest *)request withContentHandler:(void (^)(UNNotificationContent * _Nonnull))contentHandler {
   
   self.bestAttemptContent = [request.content mutableCopy];
   
   self.bestAttemptContent.badge = @20;
   self.contentHandler(self.bestAttemptContent);
   

   }

Don't know what I am missing here. Searched and followed so many documents. Nothing seems to be working.

I am using XCode 11.2.1 and real device with ios version 13.