I think it was @Nyrhi or @Nulwraith I cant remember but apparently according to https://github.com/wizjany/worldedit/commit/ca1cecbdf433104465ae4597ef56890f9bed6326 the //flip command was having issues and they may have fixed it in that commit to worldedit so when we can confirm all of our plugins will update fine then you will see that start to work again.
I think it was @Nyrhi or @Nulwraith I cant remember but apparently according to https://github.com/wizjany/worldedit/commit/ca1cecbdf433104465ae4597ef56890f9bed6326 the //flip command was having issues and they may have fixed it in that commit to worldedit so when we can confirm all of our plugins will update fine then you will see that start to work again.