Created Unassigned: Problem about set font more 506 row. Please help me [12703]

I try set font more 506 but npoi can't set. i don't know

Code
IFont font = _sheet.Workbook.CreateFont();
font.FontName = fontName;
font.FontHeightInPoints = fontSize;
ICellStyle style = _sheet.Workbook.CreateCellStyle();
style.SetFont(font);

foreach (var cell in _sheet.GetRow(row - 1).Cells)
cell.CellStyle = style;

Please help me
Thank you