My friend and I are playing on a multiplayer region. We were able to set up our colonies without problems. Upon exiting, (going to main menu or going to the region screen) the cities do not show up on the region, even if directly clicking the "save" button before leaving. However the cities are not lost: we cannot put a new city in the place of the hidden old cities, but we can put new cities on untouched land.
Addendum: on the region screen, it displays the amount of power and atmosphere of the old city at the top, but the other resources are at their default.
yes, this is a known thing for many, and if i am correct it has been posted before letting bast know, currently multiplayer region is experiencing a lot of bugs and well actually major bugs, and so unfortunately either that it currently does not work correctly.
Be sure to join the NOZ discord!