EPPLus don’t read default height from excel

When I’m trying to read default height by EPPlus it always returns me 15. I was checked, function GetXmlNodeDouble returns number, but there are another function, where are function returns ” “.

public double DefaultRowHeight
        {
            get 
            {
                if(double.IsNaN(_defaultRowHeight))
                {
                    _defaultRowHeight = GetXmlNodeDouble("d:SheetFormatPr/@DefaultRowHeight");
                    if(double.IsNaN(_defaultRowHeight))
                    {
                        _defaultRowHeight = 15; // Excel default height
                    }
                }
                return _defaultRowHeight;
            }
            set
            {
                _defaultRowHeight = value;
                SetXmlNodeString("d:sheetFormatPr/@defaultRowHeight", value.ToString(CultureInfo.InvariantCulture));
                SetXmlNodeBool("d:sheetFormatPr/@customHeight", value != 15);

                if (double.IsNaN(GetXmlNodeDouble("d:sheetFormatPr/@defaultColWidth")))
                {
                    DefaultColWidth = 9.140625;
                }
            }
        }

internal double GetXmlNodeDouble(string path)
        {
            string s = GetXmlNodeString(path);
            if (s == "")
            {
                return double.NaN;
            }
            else
            {
                double v;
                if (double.TryParse(s, NumberStyles.Number, CultureInfo.InvariantCulture, out v))
                {
                    return v;
                }
                else
                {
                    return double.NaN;
                }
            }
        }