[Update 7/22]
This issue has been resolved. The NA Reboot world is now available to log in and play. Thank you for your patience.
[Original Message]
We are currently investigating an issue causing channels to crash in NA Reboot, as well as rollback issues players may have experienced. Until the channel crash issues have been resolved, the NA Reboot world servers have been taken offline and will be unavailable temporarily. We apologize for the downtime and will provide updates on our web announcement here: https://maplestory.nexon.net/news/75590