Logs have this pertinent line:

[10:24:55] [Render thread/FATAL]: Error during pre-loading phase
net.minecraftforge.fml.ModLoadingException: Mod File HammerLib-1.20.1-20.1.13.jar needs language provider javafml:47.1 or above to load
7We have found 47

Downgrading to previous version allowed the game to load. Forge version was 47.1.47.