I've got a very weird situation.
Obviously on my development machine Nancy.Serialization.JsonNet loads properly in my project.
However, in production Nancy.Serialization.JsonNet does not load.
I can confirm the assemblies loaded using Sysinternals Process Explorer, and my initial review of the FusionLogs in production do not indicate a problem. However, I do have a "Total # of load failures" count of 1 in production, and 0 in development.
I'm not expecting a solution to this, at the moment; just putting something here for the google gods for the other poor souls who have to spend 5 days tracking this down.
I've tried upgrading the project to .NET 4.6, down to 4.0, nothing.
I think I'm going to have to manually return JSON strings, and manually handle them in my client library for now. Bummer!