Add to Siri error - cannot handle shortback controller

I am integrating a function “Add to Siri” that would make life easier for a lot of iOS users. However, I have a roadblock that needs to be addressed first. I have to handle a shortback controller inside this delegate:
INUIEditVoiceShortcutViewControllerDelegate & INUIAddVoiceShortcutViewControllerDelegate
Error on this is:
func addVoiceShortcutViewController(_ controller: INUIAddVoiceShortcutViewController,
didFinishWith voiceShortcut: INVoiceShortcut?,
error: Error?)
What might be causing the error?