Could not load or find assembly. A strong named assembly is required error when running unit tests

I'm converting a .NET Framework 4.5.1 test project from the older csproj file format to the newer vs2017 format. In doing so, I am able to build but am receiving an error when attempting to run unit tests. Only 7 tests from the project are failing. I'm not sure if I am missing a NuGet dependency?

I've already tried turning off signing for the project- which worked but I have a constraint of requiring signing.

System.IO.FileLoadException: Could not load file or assembly 'DDay.iCal, Version=1.0.1.490, Culture=neutral, PublicKeyToken=null' or one of its dependencies. A strongly-named assembly is required. (Exception from HRESULT: 0x80131044)``````