You must upgrade your ACS compiler to use ACSUtils because the official ACC 1.55 release can't compile files with more than 256 functions.
Upgrade to one of the following compilers:
acsutils.acsto your project.
#include "zcommon.acs" #include "acsutils.acs"
If your project has functions (or variables, if you are using ACC) with the same names as ACSUtils functions, it won't compile. Rename the functions in your project to fix it. ACSUtils functions are named to avoid some of the most annoying conflicts, but it still needs several renames in some big projects.
cvarinfo.acsutilsto your project root to allow the server to hide ACSUtils errors using the
acsutils_noerrorscvar (it will automatically load and not conflict with your mod's CVARINFO because ZDoom ignores the extension).