Sitting with an interesting problem. .NET 4.5 is not supported on the server (client didn't mention this)
BUT the app is written using ASP.NET MVC 5 (which only runs on .NET 4.5).
So downgrading the dot net means to downgrade the ASP.NET MVC version.
One of the many errors we are getting is
The type or namespace name 'Mvc' does not exist in the namespace 'System.Web'
I can only assume this is due to the implementation of all the Owin middleware in ASP.NET MVC 5.
Has anyone had any experience with removing these references and being ASP.NET MVC 4 capable?
Following Greg's suggestion below I ran the nuget which removed v5, and added in v4, but now all the Owin stuff is an issue