To check your file - please open your file in a text editor rather than excel to check it looks ok and is not empty. Depending how your file was crerated, opening the file in excel and saving it as a csv again may resolve some errors. This error is given when UpSheets is unable to process your file because the first row of your file does not contain the header fields. This is usually because the file has text in the first line when UpSheets is expecting header fields separated by commas. The below is ok: The below is not: To resolve this, remove the first line and save the file, then try again. If you require text lines in your file, such as notes but do not wish to import them you can put a # at the start of the line and it will be ignored, ie: