A perfectly valid message from a potential buyer was incorrectly put in the Spam folder by Etsy. As I don't receive notifications for Spam messages, I didn't see it until much later. As soon as I moved it to the Inbox, I replied immediately. Etsy then marked down my 100% message response rate because of this message. If Etsy makes a mistake in marking a message as Spam, it hardly seems fair to penalise the recipient for not responding quickly.
@IGPhotoStore: The only thing we can suggest is to read the "solution" posted by an Etsy moderator on https://community.etsy.com/t5/Technical-Issues/Star-Seller-Rating-Affected-Due-to-Etsy-Putting-Messa...
While they may say they are working to correct the problem, I wouldn't hold my breath. They messed mine up once on an order saying it had no tracking when it clearly had tracking that was even purchased through Etsy. Yet they counted it as no tracking. I nagged them for weeks about it and they finally admitted that they were aware of the "glitch" but had no date for a resolution. In other words, too bad, so sad, move on. Some say they have had theirs changed. But I think the program generating the data may have many limitations that prevent them from altering the results.