Error 500 when trying to Upload Video with Xmlhttprequest Asp.net/C#

Question

I have an application that uploads video using XMLHttpRequest when I uploaded a small video (386Kb) the video goes up normal, but when I try a larger video (20Mb) it does not reach the function C# and returns error 500.

This is my Front End function :

document.getElementById('formItem').onsubmit = function (e) {

    var formdata = new FormData(); //FormData object

    //Creating an XMLHttpRequest and sending
    var xhr = new XMLHttpRequest();

    xhr.addEventListener("load", transferComplete, false);
    xhr.addEventListener("error", transferFailed, false);

    xhr.open('POST', '/Unidade/Item/Cadastrar');

    if (xhr.upload) {
        xhr.upload.onprogress = function (e) {
            if (e.lengthComputable) {
                console.log(e.loaded);
                var value = Math.floor((e.loaded / e.total) * 100);
                progressBar.style.width = value + "%";
                progressBar.innerText = value + "%";
            }
        }
        xhr.upload.onloadstart = function (e) {
            progressBar.value = 0;
            display.innerText = '0%';
        }
        xhr.upload.onloadend = function (e) {
            var percentComplete = (e.loaded / e.total) * 100;
            $('#progressBar').css({ 'width': percentComplete + '%' });
            loadBtn.innerHTML = 'Iniciando o Upload';
        }
    }
    xhr.send(formdata);
    return false;
}

error returns when I call xhr.send(formdata);, the smaller video reaches the method normally but the biggest of the error, the two has the same extension (.mp4). If any information is missing let me know.

video input :

 <video  controls poster="/Content/imagens/principais/Video-PlayButton.png" >' +
        <source src="' + e.target.result + '" type="video/mp4">

  </video>