I am in the UK. I have changed the region, language, keyboard and system locale all to US English and it still flippin doesn't work. Says Cortana is not available for your market. What am I doing wrong? Am on latest build on Dell Venue 8 Pro tablet.
I had this same problem you need to change your system language as well. After I removed English UK and English Australia as options Cortana started fine.
I wish MS didn't pull this sort of crap to get Cortana working. I just want a voice assistant.