Call non-static member of static property in static class with reflection

I have a static class which looks for an implementation of an abstract type and stores it as a static property similar to the below:

public static class MyStaticClass
{
    private static MyAbstractType _MyAbstractImplementation;

    public static MyAbstractType MyAbstractImplementation
    {
        get => _MyAbstractImplementation ?? ( _MyAbstractImplementation = FindImplementation());
        private set => _MyAbstractImplementation = value;
    }
}

And I am trying to call a method of MyAbstractImplementation (which contains no static properties or methods) via reflection:

var myAssembly = Assembly.Load("MyStaticClassAssembly")

var myType = myAssembly.GetTypes().First(t => t.Name == "MyAbstractType");

var myImplementation = myType.GetProperties()
    .First(p=>p.ReflectedType?.Name == "MyAbstractImplementation")
    .GetValue(null);

var obj = myType.GetMethod("SomeMethod")?.Invoke(
                null,
                new object[] 
                {
                    // Some args
                });

The above code causes the following exception on getting the value of MyAbstractImplementation:

System.Reflection.TargetException: Non-static method requires a target.

Evidently, this is because I am passing null to GetValue(), so I try passing myAssembly rather than null and I get the following exception:

System.Reflection.TargetException: Object does not match target type.

Out of desperation, I try passing myType and myImplementation but I still get the same exception.

What am I meant to be passing to GetValue()?