try using the experimental version, here's a tutorial on how to make it work: GUIDE ON HOW TO INSTALL AND PLAY CLAN-GEN EXPERIMENTAL VERSION : r/WarriorCats (reddit.com) hope it helps! I had the same problem.
"Experimental version" has not been a thing for several months now and is now called developmental version. You also cannot get official tech support on the discord with source versions, and this guide is generally a bit outdated and not really the best way to play the game, even if you want to play source versions.