I have tested your scenario and it works fine. I created a new workbook, create the style and specify the font attribute (set bold etc.), apply the style, and finally save the workbook. I don’t find any issue with the output file (attached).
Here is my sample code:
//Instantiating a Workbook object
Workbook workbook = new Workbook();
Worksheet worksheet = workbook.Worksheets;
Cells cells = worksheet.Cells;
//Adding the current system date to “A1” cell
Aspose.Cells.Cell cell = cells[“A1”];
//Setting the format of the cell.
Style style = new Style();
style.Font.IsBold = true;