The following are possible causes.
- You are playing on another device.
The game cannot be played on multiple devices at the same time with a single MJM-ID.
- When you quit the game without "log out" on the last device you played on.
You will not be able to log in from other devices for 2 hours.
*You can log in by performing "logout" on the device you played last time.
In either case, you will be able to log in after about 2 hours, please try again later.