My message response rate os showing as lower because I didn't message my son after he made a trial purchase to ensure digital downloads were working. Is there anything I can do about this? Obviously didn't realise the significance at the time and that it would impact on me becoming a Star Seller.
You could send his message to spam. That's about all you can do. Your star seller rating should go back up in a day or so.
@Vibrantverse: If the unanswered new thread is not a Help Request, at least for the time being, it appears that marking an unanswered message as SPAM (even after the 24 hour deadline has passed) will cause your reply percentage to change in a day or two if the original message was within the current star seller period (but not retroactively). Note that subsequent messages from that account may go directly to the SPAM folder.
Keep in mind that the Star Seller metric is that the first message of a EVERY new incoming thread must be replied to within 24 hours. It does not matter who sent it, the subject matter, if it is a duplicate or blank or anything else. If it is SPAM then it should be marked as such.