Why as a seller am I being told that I did not respond when I did respond?
If a reply is not sent back through our system after several days we will send the seller an automatic message to remind them. Each inquiry by a user on a different ad should receive a unique response.
Perhaps you responded to these emails another way, like phone. In this case, visit your messages page and click reply and "Responded Elsewhere." This will keep your account looking responsive to users and prevent future reminder emails.