You cannot convert Excel workspace files (.xlw) to actual .xlsx spreadsheets. A workspace is just a setting for the program so it knows where to put various tools offered by Excel. You can apply workspaces inside the program, but not save it as spreadsheet, which means xlw to xlsx conversion is not possible.
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.