I left the city on all the trains on Saturday at 20:30. On Sunday at 20:31, the number of active players in the city did not change even after the game was restarted. There was no change even at 21:01, when the recalculation of factory occupancy was. So when will it be evaluated that I left the city (I stopped supplying anything to it) more than 24 hours ago?
Maybe another player starts to deliver something to your city ? You don't know, because the list of connections doesn't show who is active and who isn't.