Dream Drop Distance Glitch
Kingdom Hearts 3D has a glitch that halts the progression of the game. Square-Enix has completely acknowledged the issue on their Square Enix’s Online Support Site. Square suggests that if you encounter the bug to load from a previous save file. If you do not have one, you should contact their information center. According to SQEX GAL, this is the specific condition.
It looks like there is a glitch when you play as Riku in a certain part of the World That Never Was. If you drop as Riku in a certain spot where stairs appear but before you can go up them, when you return you will be locked out and and unable to progress, thus the warning.