Outlook Web Add-in邮件转附件功能故障排查求助

我的Outlook Web加载项无法正常运行，执行到// Get the selected email message步骤后无任何响应。控制台报错：Uncaught (in promise) SyntaxError: Unexpected token 'H', "HTTP/1.1 4"... is not valid JSON。

需实现的功能：用户输入一个数字作为新邮件的主题，将选中的邮件作为附件发送至recipient@recipient.com。相关代码如下：

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8" />
    <title>Ask Dossiernr</title>
    <script src="https://appsforoffice.microsoft.com/lib/1/hosted/office.js"></script>
    <!-- Office UI Fabric CSS -->
    <link rel="stylesheet" href=https://appsforoffice.microsoft.com/fabric/2.1.0/fabric.min.css />
    <link rel="stylesheet" href=https://appsforoffice.microsoft.com/fabric/2.1.0/fabric.components.min.css />
</head>
<body>
    <div class="ms-welcome">
        <form id="emailForm">
            <p class="ms-fontSize-l ms-fontWeight-light ms-fontColor-neutralPrimary">Vul het dossiernummer in en klik op de knop om te versturen. V1.8</p>
            <br />
            <input type="text" id="dossierNr" class="ms-TextField-field" value="1234567">
            <br /><br />
            <button id="verzenden" class="ms-Button ms-Button--primary">
                <span class="ms-Button-label">Versturen</span>
            </button>
        </form>
    </div>
<script>
    (function () {
        Office.initialize = function (reason) {};

        // Add click event listener to the "Versturen" button
        document.getElementById("verzenden").addEventListener("click", function () {
            var dossierNr = document.getElementById("dossierNr").value;
            console.log(dossierNr);
            console.log("clicked");

            // Get the selected email message
            Office.context.mailbox.item.getSelectedDataAsync(
                Office.CoercionType.Html,
                function (asyncResult) {
                        console.log("getSelectedDataAsync callback called");
                        console.log(asyncResult);
                    if (asyncResult.status === Office.AsyncResultStatus.Succeeded) {
                        // Create a new email message with the selected email as an attachment
                        var newEmail = Office.context.mailbox.item.createReplyAll();
                        newEmail.to.setAsync(["receiver@receiver.com"]); // Add recipient
                        newEmail.subject = dossierNr;
                        newEmail.body.setSelectedDataAsync(
                            asyncResult.value,
                            { coercionType: Office.CoercionType.Html },
                            function (asyncResult) {
                                if (asyncResult.status === Office.AsyncResultStatus.Succeeded) {
                                    // Add the selected email as an attachment
                                    var attachment = {
                                        type: Office.MailboxEnums.AttachmentType.Item,
                                        itemId: Office.context.mailbox.item.itemId,
                                        name: "Original Email",
                                    };
                                    newEmail.addFileAttachmentAsync(
                                        attachment.itemId,
                                        attachment.name,
                                        { asyncContext: attachment },
                                        function (asyncResult) {
                                            if (asyncResult.status === Office.AsyncResultStatus.Succeeded) {
                                                // Send the new email
                                                newEmail.send();
                                            } else {
                                                console.error("Error adding attachment: " + asyncResult.error.message);
                                            }
                                        }
                                    );
                                } else {
                                    console.error("Error setting email body: " + asyncResult.error.message);
                                }
                            }
                        );
                    } else {
                        console.error("Error getting selected email: " + asyncResult.error.message);
                    }
                }
            );
        });
    })();
</script>
</body>
</html>

内容的提问来源于stack exchange，提问作者Crikkelieke