The new encryption is finnicky. If the editor misaligns a single byte, your save will show "Download Failed. Please restart the game." Unlike the old days, there is no cloud backup; you will start from zero.
Ensure PvZ 2 is completely closed and not running in the background. pvz 2 save editor new
Unlock all plants (including premium ones), change their levels (including Mastery levels), and add costumes. The new encryption is finnicky