Nintendo has taken the Super Mario Maker network offline for an estimated 37 hour maintenance to address a “Create” bug.
The network went offline already and is expected to return on Thursday, 28th January at 5pm Pacific / 8pm Eastern and 1am UK (29th January).
The announcement reads
We are carrying out emergency maintenance to fix a bug that occurs in “Create” mode. During this time, Super Mario Maker’s online services will be unavailable
To be offline for such an extended period of time, the issue being addressed must run pretty deep within the system or the network was taken down before the fix was created to prevent abuse/problems for players.
Super Mario Maker is available now for the WiiU.