Curse, Forest’s Curse, Power Trick, and String Shot seem to have been fixed and are no longer banned from Pokémon competitions.
☆ NintendObs Weekly – Monday, February 5, 2018 – Sunday, February 11, 2018.
Play! Pokémon Video Game Rules Update
The recent move bans have been lifted from Play! Pokémon video game tournaments.
February 07, 2018
Pokémon Ultra Sun and Pokémon Ultra Moon have been updated to version 1.2. The moves Curse, Forest’s Curse, Power Trick, and String Shot are no longer banned from Play! Pokémon video game tournaments. The new update is required to play in tournaments. To update your game, visit the Pokémon Ultra Sun or Pokémon Ultra Moon entry on Nintendo eShop and then download the latest patch.
The full rules can be found on the Play! Pokémon Rules & Resources page.
— Pokémon News