I am trying to update sales order via csv for the same item, when I add different item it adds it but when I adds the same item it says import successful but nothing happens on sales orders

are you trying to add a new line for an item that's already on the sales order? IIRC: Try mapping the "Line ID" field, but set it to blank for the line(s) you're wanting to add. This way the CSV import will know that it should be added as a new line. Without "Line ID" mapped, the CSV import will try to use the item field to match an existing line with the same item (hence why uploading a different item resulted in a new line, as it couldn't find a match)

That worked, I forgot to update here @Sam-I-Am to rescue

@Sam-I-Am will not eat green eggs and ham