Why I cannot use Pages ???

Everyone else can use Pages OK, so you need to find out what is not right in your particular situation..

To get help with that here, you need to provide more details about exactly what is happening when you try to use the app.

Intro to Pages on iPad - Apple Support

From Google Translate: "There was a problem displaying the documents. Retry"

You need to tell us exactly what you did to get that message on your screen, and what kind of document you are trying to display.

Pia2304 wrote:

I try to open the Pages, but it doesn't work

.

Are you doing that by tapping the Pages icon?

Have you tried restarting your device?

Force restart iPad - Apple Support

Do you speak Vietnamese? If so, please provide an English translation of what it says on your screen.