The issue occurs when there is a mismatch between your Battle.net desktop client language and your in-game language settings. Instead of saving the localized files permanently, the launcher treats them as missing asset packages, triggering an unending verification loop. Exclusive Fixes for "Preparing Game Data" 1. Sync the Launcher and In-Game Languages
Under the section, check the boxes for both your current preferred language and any language you have previously used. starcraft 2 preparing game data exclusive
When the game cannot find the active localized assets on the local drive, it forces an on-demand download loop. The issue occurs when there is a mismatch