I see you have an ID column … are you, by chance mapping that to the Entry ID field? It sounds as if you are importing this for the first time, is that correct? If that is the case, you can not map to the Entry ID field because those entry ID/s do not exists. The ID/s will have to match those that are created by the WP data base after the CSV is imported. If you are mapping it to the Entry ID field… the importer will open the ID and attempt to up that entry with the new data and since that entry ID does not exist, it can not be updated.
Hope that helps!