Not able to run a project referencing to private nuget package

I have a project which has a dependency on Azure functions, class libraries and private NuGet packages.

I am trying to benchmark a method inside a service class. But I am getting the below error

 Build Exception: C:\Program Files\dotnet\sdk\3.1.100\NuGet.targets(123,5): error : Unable to load the service index for source https://pkgs.dev.azure.com/.../index.json. [C:\..\Benchmarking\bin\Release\netcoreapp2.1\e50243bd-a276-4e7c-b2bc-33b3959a1b2c\BenchmarkDotNet.Autogenerated.csproj]
C:\Program Files\dotnet\sdk\3.1.100\NuGet.targets(123,5): error :   Response status code does not indicate success: 401 (Unauthorized). [C:\..\Benchmarking\bin\Release\netcoreapp2.1\e50243bd-a276-4e7c-b2bc-33b3959a1b2c\BenchmarkDotNet.Autogenerated.csproj]

I am not sure why this error is happening as we are taking nuget packages from cache when running a project.

Please let me know if you need more information on the project or error.