I'm not really sure if I'm doing something wrong or if there's an error in the mod that I just need to wait to be resolved, but here's some info that might help:

Minecraft: 1.17.1
Fabric Loader: 0.11.7
Mods:

Windows 11 Pro: 21H2 (22000.318)

Duplicate of #374

This has (finally) been fixed with OptiFabric v1.11.22, you'll want to update to the (current) newest OptiFabric version here.

i have 1.16.5 but I get this error in developer console
-- OptiFabric --
Details:
OptiFine jar designed for: NULL
OptiFine jar version: NULL
OptiFine jar status: Not found
OptiFine remapped jar: NULL
OptiFabric error: OptiFabric could not find the Optifine jar in the mods folder: