Who can i make a Superflat Server on Nitrado

Was there an existing world save prior to setting that flag? It has to be on a new world (meaning set it before starting the sever and generating the world for the first time) otherwise its likely going to ignore that flag and look at whatever value is set in the sql file for the world save.

If you have nothing built yet you can probably shut down the server, wipe the Worlds directory and start up again.

My server is on Nitrado. I setup the world in Single Player mode (where you could create a "Superflat" world), then copied the World files up to the server.