E-mail incidents reach Closed status for a couple of reasons, as outlined below. Please note that Closed status does not indicate that an issue has been resolved.

No response from you within 72 hours:
When you do not respond to an incident within 72 hours, it is automatically set to Closed status. This does not mean that we consider the issue resolved. It only means that we did not receive a response from you within 72 hours. We understand that there will be times when you will not be able to respond within 72 hours. If your incident is closed in error, you may update it in the My Stuff section of the NCsoft Support Website. This will re-open your incident. You can also update it by following the instructions at the top of the last e-mail that you received from support.

NCsoft staff manually sets incident to Closed status:
When appropriate, our staff may set your incident to Closed status. They will send an explanation for the status change. For example, if you have more than one incident regarding the same issue, a representative may combine the information from all open incidents into one incident and close the others.