Updating existing products
For, to update an existing product in the OpenCart catalog, sure to choose Key field in section Products > Import expansion, by which the product will be identified and the presence of this field in the CSV file
Product update is carried out in modes Update only and Update and Add
For example, if the Model key field is selected (_MODEL_), then in the file this field must be present.
All products will be imported from a CSV file according to the selected import mode.
More on import modes