Thanks for your interest in Aspose.
I was able to reproduce this bug using the latest version:
Below is my code and I have attached the output html file.
This issue has been logged as CELLSNET-29153.
string path = @“F:\Shak-Data-RW\Downloads\Files\2a5064e4-56ba-476a-acd2-93b037112ae2.xml”;
Workbook workbook = new Workbook(path);
workbook.Save(path + “.out.html”, SaveFormat.Html);
We have now supported saving conditional-formatting to html in the latest aspose version.
Please download: Aspose.Cells for .NET v220.127.116.11.