Ensure you have the Update 1.2 CIA file (ensure the region matches your game, e.g., USA, EUR, or JPN).
: For those using custom firmware, the update is often found as a file. Tools like pokemon ultra sun update 12 3ds world cia portable
and its updates are often categorized as "World" or region-free because the Title ID is frequently the same across different global releases, allowing a single update file to work on various regional versions of the base game. Where to find it: Official updates are typically handled through the Nintendo eShop Ensure you have the Update 1