I just done a windows 10 install on a Samsung all in one computer and Cortana was an option to install. I tried it and it seems to work. didn't have any trouble understanding my voice. I had to make sure I said open then the program on the computer I wanted otherwise it opened up a web browser and searched for what ever I said.
Just checked all my computers. (all set to NZ region and NZ English)
Windows 10 says: Cortana isn't supported in the region and language you've selected.
What region and language have you set up on the computer?