Why when I use eyedropper to the white color it doesn't white on the ring?

Hey, @V�_Danh2112. Welcome to the Photoshop Community. I'll help you figure this out. 

This is a common issue. Have you imported this document, or was this made in Photoshop on the same machine? 

Here is a conversation that can help you: https://adobe.ly/40FxmKI

If this does not help, comment back here and we'll continue to help you. 

Thanks!