accessing c# web assembly from javascript in .net MVC

I need to access some c# code from javascript in MVC ,NET (not blazor).
I have the below. I get no error message it just continues to the next statement after the ajax call. There could be 2 possible issues i think. My url: ‘/Home/CreatePostcodeFromCoordinates’, is wrong.
Or my C# assemply is not part of the assembly? or something similar. I am not that experienced with Web techs, I come from a DB background but can’t be that difficult to get this link working right? Can’t see anything else wrong. Also does the return value from C# need to be some special format or a string (as per now) is ok? this could be another reason?
Thank you!

console.log("just before /Home/CreatePostcodeFromCoordinates");

$.ajax({
    type: "POST",
    url: '/Home/CreatePostcodeFromCoordinates',
    data: { param1: longitude, param2: latitude },
    success: function (response) {
        console.log('success');
        console.log(response);
    },
    error: function (error) { 
        console.error(error);
    }
});