This is Happy Wars Management Team.
The update data released on May 29th for Xbox One and Windows 10 has not yet been released on Xbox 360. Due to the difference in versions, the cross-save function between Happy Wars for Xbox 360 and Happy Wars for Windows 10/Xbox One is temporarily available only one way.
Players can access their Xbox One and Windows 10 accounts even if they have recently played Happy Wars on Xbox 360 with the same account. However, Players who have played on Xbox One or Windows 10 versions of Happy Wars will be unable to access the same account on Xbox 360.
The latest update for the Xbox 360 version of Happy Wars will be released very soon. Once released, players will be able to access the cross-save function normally.
We apologize for any inconvenience caused.
We hope to see you on the battlefield in Happy Wars again soon.
Regarding cross-save between Xbox 360 and Xbox One/Windows 10