I have OC 1.5.6.1 and E/I 17 and I downloaded a spreadsheet no problem. I even used OpenOffice as suggested. I added some products to the spreadsheet and tried to re-upload. But I got the error. I changed nothing else. I added the products by copy & pasting data from an older version of E/I from my 1.4.9 store.Uploaded file is not a valid spreadsheet file or its values are not in the expected formats!
Also when you save an OpenOffice document .ods you can't save it as an xlsx file so you can't import it again. So using OpenOffice seems pointless?
This is driving me crazy