App Part - Unable to read file after upload. Access Denied.

I am following the MSDN article, "Code example 1: Upload a file across SharePoint domains by using the REST API and jQuery" found here.

The file actually upload pefectly; however, when it tries to process the 'getListItem' function so that the file can be renamed, I receive an 'Access Denied.' error. I have checked to make sure that the app part has write permissions and that even on the list 'everyone' is given permissions (I know this is not need, but I wanted overkill).

I cannot figure out why it can upload to a folder and then not read from the same location? Any ideas?

Below is the code in question:

    // Get the list item that corresponds to the uploaded file.
    var getItem = getListItem(file.d.ListItemAllFields.__deferred.uri);
    
    // Get the list item that corresponds to the file by calling the file's ListItemAllFields property.
    function getListItem(fileListItemUri) {
        // Construct the endpoint.
        // The list item URI uses the host web, but the cross-domain call is sent to the
        // add-in web and specifies the host web as the context site.
        fileListItemUri = fileListItemUri.replace(hostWebUrl, '{0}');
        fileListItemUri = fileListItemUri.replace('_api/Web', '_api/sp.appcontextsite(@target)/web');
    
        var listItemAllFieldsEndpoint = String.format(fileListItemUri + "?@target='{1}'", appWebUrl, hostWebUrl);
        // Send the request and return the response.
        return jQuery.ajax({
            url: listItemAllFieldsEndpoint,
            type: "GET",
            headers: { "accept": "application/json;odata=verbose" }
        });
    }