Q: No FaceTime ?

If you’re running Mac OS X 10.7 or newer, it’s already in the Applications folder, doesn’t need to, and cannot be bought separately.

If you’re running Mac OS X 10.6, what happens when you try buying it?

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FaceTime is not available in Saudi Arabia, Pakistan, and United Arab Emirates, including Dubai.

See also Get help if you can't make or receive FaceTime calls - Apple Support

If you use a different store then I'm not sure why you cannot get it.

tt2