Artillery does not work after upgrading my server to v8.0.3.

v8.0.3 added a new package, DH_Artillery. Due to the way the introducing new packages are handled in the UT2004 engine, you must manually edit your server's existing configuration file to have them loaded. To fix this, follow these steps:

1. Open your server's /System/DarkestHour.ini file.
2. Navigate to the [Engine.GameEngine] section.
3. Add the following line to the bottom of that section:

ServerPackages=DH_Artillery

4. Save the file.

Note that deleting your /System/DarkestHour.ini will also fix the problem, but any custom server settings (including passwords, mutator lists etc.) will be wiped out in the process, so it is not recommended.