unable to add reference to installed nuget package?

I created a NuGet package and I was able to successfully install it in another .NET solution. But I'm not able to add a reference to the NuGet package from the other .NET solution. For example, let's say that the NuGet package has a class with a namespace like MyCorp.SecurityApi. I'm currently not able to add a using directive for that namespace in my other .NET solution. For example, the following using directive returns a compilation error of "The type or namespace 'MyCorp' could not be found":

using MyCorp.SecurityApi;

Any idea what the issue might be or how to debug?