The fastest way to bulk update your products in Shopify is via CSV. In order to have a properly structured document, you will need to edit it exactly by the Shopify’s standard. That means if you are just starting your import for the first time, you need to download Shopify’s sample .csv file, or if you have downloaded it previously, you will need to update your changes via “Products -> Import”.
Even if you just updated one character and tried to upload the file back you may encounter a similar error message:
Please fix the following errors: Unquoted fields do not allow \r or \n (line 2). Invalid CSV Header: Missing headers Title.
Presuming your document is properly structured, you are probably using a program like Numbers (for Mac) or Excel. Use a different program that is better suited for editing the .csv files (for example Google Sheets) and your problem will be solved.