Check the file structure before submission
Use attribute names in the first row, one product per following line, and tabs between attributes. Avoid trailing tabs and embedded tabs or line breaks in field values. Grouped and repeated attributes have their own delimiter rules; check the specification rather than guessing. Google: Tab-delimited requirements.
Reopen the exported copy and compare several known IDs and values with the original. Then submit it through your normal Merchant Center process and review the processing result. Manual uploads do not synchronize later source-file changes automatically. Google: Add products from a file.