Thanks for your posting and using Aspose.Cells.
We have tested your issue with your provided excel file (which you provided in this post i.e. 832365 in reply to 832188) with the following sample code using the latest version and did not find any issue.
Please check the attached output html generated by the code and screenshot that compares the output with your source excel file.
If you still find any issue, then please provide us your exact sample code (it should be runnable code not just code snippets) and if we are using some different sample excel file, then also provide us your actual excel file.
Workbook workbook = new Workbook(“extra_sample.xlsx”);
Worksheet ws = workbook.Worksheets[“Arkusz1”];
workbook.Save(dirPath + “output.html”, SaveFormat.Html);