Your import results display skipped lines?
There are various reasons.
The identification action is incorrect:
Solution: select the correct action: create or modify products
The identifier selected does not exist in the catalog when 'modify products is selected
Solution: check that the exact identifier exists in the catalog
The identifier selected exist in the catalog, and action for existing products is on "skip"
Products descriptions and/or meta descriptions include carriage returns
Solution: Importing descriptions
The number of lines to process in the CSV file is greater than the number of line used in the configuration.
Solution: increase the number to match your CSV file.
If you work in Multistore mode, make sure the products to modify exist in the id_shop_list specified in your CSV file.