Secure Write iOS 10.x not working

[mlfarrell]

Tried everything

  constructor() {
    super({
      uuid: 'xxxxx', //removed from post
      properties: [/*'read',*/ 'write', 'notify'],
      secure: ['write'],
    });

    this._updateValueCallback = null;
    this._value = new Buffer(0);
  }

iOS app keeps failing with Error Domain=CBErrorDomain Code=0 "Unknown error." UserInfo={NSLocalizedDescription=Unknown error.}