Prior to ASP.NET Core, MVC and WebAPI were mainly separate libraries.
The .Mvc namespace applies to MVC controllers, the .Http namespace to Web API controllers.
What is the different between System.Web.Http.HttpPut Vs System.Web.Mvc.HttpPut
They belong to two different frameworks. The pipeline flow of each is looking for specific attributes that belong to their respective namespaces.
The routing engine for the respective frameworks are not aware of the other so if a Web API attribute is used on a MVC action it would be just as if there were no attribute at all, hence the 405 error encountered.
Make sure that the correct namespace is used on the correct controller type. If both namespaces are being used in the file then be specific by calling [System.Web.Http.HttpPut] for Web API actions
[System.Web.Http.HttpPut]
public IHttpActionResult Put([FromBody]MyModel model) { return Ok(); }
and [System.Web.Mvc.HttpPut] for MVC actions
[System.Web.Mvc.HttpPut]
public ActionResult Put([FromBody]MyModel model) { return View(); }