I am so sorry you got that error. That's an error to do with Godot 4 and how it handles multi-threading. It relates to the web browser or website you are using, and whether or not they support Shared Array Buffer functionality. Since itch can support it, and it is set to do so, it most likely means the web browser you are using does not. Would you mind telling me what browser you are using so I can look into it?
edit/TLDR: The web browser you are using most likely can't run HTML games made in Godot 4