After I logged out and again logged in, all the maps disappeared.
Does anybody have any knowledge about this?
Another user faced the same issue earlier and resolved it by clearing cache. Please try doing this.
Otherwise, check your laptop and browser are up to date. Then quit and restart your browser and log back into MindMeister. Also try opening your maps in Incognito.
If none of this works, please provide the following info:
Please grant us support access to your account. To do this: head over to your policies section in your accounts area (follow this link) to access this section directly and grant our team Support Access.