Getting related entities ASP.NET WebApi OData v4 results in “No HTTP resource was found that matches the request URI”

I followed this asp.net tutorial by Mike Wasson, and managed to set up the related entities just fine, but when I applied this logic to my project the more complex entity relations (in that there are more of them; that’s the only difference) wouldn’t succeed in an OData call, I got a 404 with this payload: