I also got the same error message.

In IOS 16 simulator, go settings -> Spoken content -> Voices -> Select any language and download. after downloading, test the app. It works for me.

before you get siriLanguageCode(), first you have to request Siri authorisation from the user you. SiriRequestAuthorization - https://developer.apple.com/documentation/sirikit/inpreferences/1829429-requestsiriauthorization.

I found the answer. First you have to get siri authorization from the user.

I tried but no luck