One common issue is when people accidentally register with the site twice. Most commonly, this happens when a member registers first with an email address and then logs in with Facebook. If the email address attached to the Facebook account is different from the one used with the site originally, a second account will be created. That second account won't have any access to the listing or messages of the first as we don't know that they are linked. To fix, log out and log in with the method used to create the listing initially.