there's an issue in eventlist extension for xmap. in latest eventlist 1.1 release the sitemap is not showing categories content anymore (on both side, html and xml).
i suppose this happens due to some little changes into the variable that calls the event ID.
Online i've found a working version of this extension but it is an hack of the content extensions so many other functions are not working like item priority and so on so it's better you check the original attached version made by the developer and work on this.
xmap version: 1.2.12-for-Jooma-1.5
eventlist version 1.1beta3.2.3-6