Display messages

[MulleDK19]

The language file is case sensitive. Use CATEGORY instead of Category.

<CATEGORY Name="DisplayMessages">
<Entry Name="IntroMessage">whatever</Entry>
</CATEGORY>

still not working

What's the rest of your language file?

The problem could also be that your function is called SetMessage, so the callback tries to call the internal SetMessage function already existing in the game, rather than yours.