Sending byte array to Speech-To-Text API (Azure)

i am recording voice on browser and sending it to my API, which is going to send data to Speech-To-Text Api (Azure).
I am keep getting NoMach from the API.

Here is my browser code:

let languageCode = "da-DK";
let mediaRecorder;
let audioChunks = [];
let isRecording = false;


function startRecording() {
    var constraints = {
        audio: {
            sampleRate: 16000,
            channelCount: 1
        }
    };

    navigator.mediaDevices.getUserMedia(constraints)
        .then(function (stream) {
            mediaRecorder = new MediaRecorder(stream);
            mediaRecorder.ondataavailable = function (e) {
                audioChunks.push(e.data);
            }
            mediaRecorder.onstop = function () {
                const audioBlob = new Blob(audioChunks, { type: 'audio/wav' });
                const reader = new FileReader();
                reader.onload = function () {
                    const audioBytes = new Uint8Array(reader.result);
                    var base64String = btoa(String.fromCharCode.apply(null, audioBytes));

                    voiceToText(languageCode, base64String);

                };
                reader.readAsArrayBuffer(audioBlob);
            }
            mediaRecorder.start();
            recordButton.disabled = true;
            stopButton.disabled = false;
            playButton.disabled = true;
        })
        .catch(function (err) {
            console.error('Error recording audio: ' + err);
        });
}

function voiceToText(myLanguageCode, wavData) {
    $.ajax({
        type: "POST",
        url: "https://localhost:7058/api/Conversation/postVoiceToString",
        contentType: "application/json", // Set Content-Type header
        data: JSON.stringify({ // Stringify the data
            LanguageCode: myLanguageCode,
            WAV: wavData
        }),
        success: function (result) {
            console.log(result);
        },
        error: function (req, status, error) {
            console.log(status);
        }
    });
}

I know my API works, and when i send test data with voiceToText(languageCode, base64String); in js then it’s also works. but when i record the data and then send, then it says NoMach.