This issue has been resolved. Characters can once again enter San Commerci to complete Commerci voyages, visit the Trading Post, and perform Sweetwater transposition.
We're aware of an issue preventing players from accessing San Commerci, causing Commerci voyages, the Trading Post, and Sweetwater transposition to be unavailable.
We're working towards making this content available as soon as possible, and any further updates will be posted to the MapleStory news page. Thank you for your patience.