Sorry, your account is not eligible for Twitter Blue at this time

You are currently ineligible for the following reason(s):

If you are getting above error while subscribing to Twitter Blue, all you have to do is check at what date you changed your profile picture/name/bio and right after 7 days, apply again for twitter blue and you will be able to do it.

It doesn't matter if you are not from US/UK and using VPN, it works just wait 7 days after you made changes.