Problem after island revert!

I made a map in creative 1 with a friend, then transferred it to uefn for some coding. I published the map, all good. Now I reverted the map back to creative 1 to make new things, because it’s easier for me (+ uefn is on my brother’s pc). And after I added the new things now I transferred it again to uefn, but the new things I added are gone! (I made a duplicate of the map)! Is there a way to transfer the new things into uefn? PLEASE HELP!!!

When you transferred the second time it had nothing on the map?
-It was just default?

No, it was the old one, before the uefn things