Why does OneNote API pages request return empty page list?

Few days ago our applications (iOS, Android and Windows) stopped getting the list of Pages from Microsoft OneNote via OneNote API request https://www.onenote.com/api/v1.0/me/notes/pages. Request returns HTTP OK and empty content. Source code Windows UWP appliaction C#-XAML (from Microsoft OneNote API example https://github.com/OneNoteDev/OneNoteAPISampleWinUniversal)

    public static string GET_PAGES_REQEST = APIENDPOINT + "sections/{0}/pages";
    public const string APIENDPOINT = "https://www.onenote.com/api/v1.0/me/notes/";
    public const string AUTHMETHOD = "Bearer";
    public const string APPJSON = "application/json";

    /// <summary>
    /// Get meta data for ALL pages under a given section
    /// </summary>
    /// <param name="sectionId">Id of the section for which the page are returned</param>
    /// <param name="token">Authentication token</param>
    /// <param name="isEncryptedOnly">View encrypted only notes</param>
    /// <remarks>  The sectionId can be fetched by querying the user's sections (e.g. GET https://www.onenote.com/api/v1.0/sections ).
    /// NOTE: Using this approach, you can still query pages with ALL the different params shown in examples above.
    /// </remarks>
    /// <returns>The converted HTTP response message</returns>
    public static async Task<List<PageApiResponse>> GetListAsync(string sectionId, string token, bool isEncryptedOnly)
    {
        var client = new HttpClient();

        // Note: API only supports JSON response.
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(Common.APPJSON));
        //client.DefaultRequestHeaders.Add("FavorDataRecency", "true");

        // Not adding the Authentication header would produce an unauthorized call and the API will return a 401
        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue
        (
            Common.AUTHMETHOD, token
        );

        // Prepare an HTTP GET request to the Pages endpoint
         var getMessage = new HttpRequestMessage
        (
            HttpMethod.Get,
            isEncryptedOnly ?
                String.Format(Common.GET_PAGES_ENCRYPTED_REQEST, sectionId) :
                String.Format(Common.GET_PAGES_REQEST, sectionId)
        );

        HttpResponseMessage response = await client.SendAsync(getMessage);

        string body = await response.Content.ReadAsStringAsync();

        if (response.StatusCode != HttpStatusCode.OK)
            throw new Exception(Errors.TranslateError(response));

        var content = JObject.Parse(body);
        return JsonConvert.DeserializeObject<List<PageApiResponse>>(content["value"].ToString());

    }

sectionId and token is correct. isEncryptedOnly = false;

Notebooks and Sections work fine. Anybody can help me?