Personal Voice not working on iPhone 13 iOS 18.1

Hello. I have an iPhone 13 running iOS 18.1. I can’t use personal voice because anytime I press create a personal voice, a pop up messages says : A one-off download of 233 MB is required to continue with Personal Voice creation. But I clearly have WiFi connected and still it doesn’t let me. I tried with a different WiFi, restarted my phone and reset my WiFi settings. Someone please help me.