Forge version is 39.0.9. FS version is 3.0.0.
When I started up Minecraft, a startup error occurred regarding your mod.

Crash report: crash-2021-12-28_12.02.03-fml.txt
Log: latest.log

It would appear you dont have placebo installed (and that's the issue)
I guess the dependency declaration is missing

It seems to work now, thanks! I'll leave this issue open in case you want a reminder to add a dependency declaration.