Build error Could not load file or assembly PublicKeyToken=null

Been on this issue for hours and can't seem to figure out why my project is reporting this error. I've installed a package from the package manager but need the assemblies to be strong named. So I created and signed the assemblies using Brutal and SN.exe. Put the assemblies back in the package areas and replaced the references on the project. Cleaned and deleted the debug build directory. The project shows the error but builds an runs, then brakes on the error. I assume there some reference somewhere but can't seem to find it. It's only 2 assemblies and 1 project so it can't be that complicated. Any help appreciated!

FileLoadException: Could not load file or assembly 'MaterialDesignThemes.Wpf, PublicKeyToken=null' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)