@Kwok Wai Sabi27514573g53o If you are using a beta version of Photoshop, the Generative Fill feature may not be available or may be unstable.
The AI Button should be located in the Generative panel. Generative Fill requires an active selection. Use a selection tool (like the Lasso, Marquee, or Quick Selection tool) to select the area where you want to use Generative Fill. After making a selection, the Generative Fill button should appear.
AdChoices