I catch post request from 3rd-side static page (generated by Adobe Muse) and handle it with MVC action.
I'm having the same problem this docs helps me to understand Model Binding https://docs.asp.net/en/latest/mvc/models/model-binding.html
I solved my problem by making sure that the property name is exact match in form field name and I also add [FromForm] attribute to specify exactly the binding source.