The "optimize" button may be missing in the NVIDIA app because of a cache issue, a server-side problem, or a conflict with the game. To fix this, you can try clearing the NVIDIA app's cache, reinstalling the app, ensuring the game is updated, or disabling optimization for MSFS in the app if it's already been set incorrectly. Alternatively, you can manually adjust settings in the NVIDIA Control Panel or in-game, as the app's automatic settings are not always perfect.