Not able to GAC smartsheet csharp sdk dll into assembly

We are trying an POC application to try and read smartsheet information. Downloaded Smart CSharp SDK Nuget package into my Class Library application in Visual Studio. But my application is failing with error that smart-csharp-sdk dll not found in Assembly . So I tried to GAC/Add assembly and I get this error "Referenced assembly 'smartsheet-csharp-sdk, Version=4.0.0.0, Culture=neutral, PublicKeyToken=null' does not have a strong name.
So I would like to know if the smartsheet dll installed via Nuget Manager is not strong named with key ?? Or what am I missing here.

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