Version 5.0.0 (Fabric/Quilt) of FerriteCore has the wrong version inside its fabric.mod.json file.

Here is the error from the Fabric Loader:
"Replace mod 'FerriteCore' (ferritecore) 4.2.1 with version 5.0.0 or later."

Inside fabric.mod.json, the version tag has 4.2.1, but should be 5.0.0.

The gradle.propeties file must have had the wrong version when the mod got compiled for version 5.0.0-fabric.
That or the jar has the wrong filename.