My app no longer showing in the suggested apps for a custom extension file

Since the iOS 13 update, I can now no longer open a file with a custom extension in my app. There used to be an option when I would open my file in the Files app or an email attachment that said Open App In... then would show my App as an option. Since the iOS 13 update, there is now just the Share to icon and it does not show my app in the list of suggested apps to open the file with. Has anyone else come across this? The app is older - in Swift 3, but still runs okay except for this problem.