Trying to open an XLbook from the Spreadsheet but that doesn't seem to work

Are you trying to open it from OneStream or from your desktop? Check the file name to be sure it is correct. It should be: NewBook.xfDoc.xlBook. Another reason I have seen this happen where the book just looks blank is if I add reports in instead of "Excel Export Items". Can you send a pic of the books configuration? It never hurts to double check you have the correct report names, if anything is spelled wrong the books just don't work, they don't give you an error