Thanks for this. Your information helped me realise I actually had no idea where GamePass had installed the game (I would have preloaded it before launch back in October 2021). Turns out it was in the hidden folder C:\Program Files\WindowsApps all along. I suspect this was the cause of the issue - the game looking for files in C:\XboxGames\Age of Empires IV that weren’t there.
Long story short, by uninstalling the game and then reinstalling into C:\XboxGames\ I was able to fix this issue and the issue with the robot narrator: Narrator Issue - I hear Text to Speech instead of lady voice over