Fabric can reject a mod set before the game starts. Read which mod requires which dependency or Minecraft version. A line like the example indicates that the installed library is outside the requested range.
Match the four versions
Check the Minecraft profile, Fabric Loader, mod and its required library. Fabric API and Fabric Loader are separate components. If a mod requests Fabric API, use the release for that Minecraft version.
ExampleMod requires ExampleLibrary >= 2.0
Installed: ExampleLibrary 1.6
Remove Forge or NeoForge builds from the Fabric mods folder. Keep one compatible copy if a mod appears twice. Apply a suggested change at a time and inspect the next error if startup still fails.
For a dedicated server, exclude client-only mods. Copy the profile before experimenting with a modpack.