(Place Resource.cfg directly inside the Mods folder.)
In 90% of cases, the mod is fine. The problem is either: sims medieval resource.cfg
To keep your Sims Medieval game stable for years: (Place Resource
For most players, the correct path is:
Priority 500 PackedFile Packages/*.package PackedFile Packages/*/*.package PackedFile Packages/*/*/*.package PackedFile Packages/*/*/*/*.package PackedFile Packages/*/*/*/*/*.package sims medieval resource.cfg