New Post: Exception when creating or loading workbook: When using relative paths, make sure the current directory is correct.

It takes a LOT of patience.

Do this: Create a new project, add the references to ClosedXML and DocumentFormat.OpenXml, put "var wb = new XLWorkbook();" on Main. If you still get the error then create an issue and attach the project so I can see the error for myself.

Manuel