sales have nothing to do with message response rate.
@Wanderkissed: "... Im assuming" Have you checked the applicable CSV file available on your Star Seller page to see which new Message threads Etsy thinks were unanswered or answered late? When you look at the file remember that that the dates / times are in UTC (not your time zone), only the first message of a new incoming thread is included (all that counts for Star Seller), and usually a new incoming thread is not included until after the 24 hour reply window has passed regardless of when you replied. Star Seller stats (and the CSV file) seem to be updated only once per day so there may be an additional day's delay. There is also a link to the actual message thread so you can verify if the data is correct or not.
Keep in mind that it takes nineteen 'answered on time' new Message threads for every one that is answered late or unanswered to be at 95%.