I'm getting a broken paths error on this pack, but this pack works completely fine with regular OptiFine. Specifically tested with the Fabulously Optimized mod pack, which includes this mod.

Optifine completely bypasses the issue that is broken paths which is simply not something that I can/will do with Resewn. There is a config you could enable in Resewn to use broken paths but it is known to cause other issues and I would recommend reporting this to the pack creator instead.

If there is anything else you think should be working but isnt, I'll need logs.

It works fine now. I think this was due to having a namespace behind the /assets/minecraft/optifine/cit/ folder, e.g. /assets/minecraft/optifine/cit/osfanpack63/, which could be a bug, but idk