No, I do have various meshes in my scene (currently behind the camera), I just moved the cube out so that you can clearly see there are no reflections as it seems like just a black cube even though it should be reflecting.
PS. Theres a skybox in my scene as well, and it should at the very least be able to reflect that?!
What is the Bounds of your Sphere Reflection Actor? The Bounds are what determines what is being reflected in the generated cubemap which is applied to simulate reflections in your material based on its Metallic and Roughness Settings. So the large yellow sphere that is visible when you click on the reflection actor is the extent of your reflections. If the reflections do not encompass an object the cubemap will not render said object in the reflections.
Hopefully that helps and if not please let me know where I can help explain further -