deleted the mc server :(

i don't know why it would work on mine if it doesn't work on yours, but i can try

the client is supposed to upgrade it to the new format if it loads successfully, you should be able to copy the modified world back up to your server and run it

server won't update an old map. you have to do it locally in single player and then put it back on the server.
I did thus. it worked and I played it locally in single player but it still shows up as old on the server