Unable download speech language in Windows 10

I had a similar problem where the only Speech language available was US English and Windows would not let me download UK English speech in order to match my Region and get Cortana to work.

I solved it with a temporary registry edit to force Windows Update to re-download all the UK language files including speech. Usual Disclaimer: "Do not attempt this unless you are comfortable editing the registry/stopping services and risking wrecking your Windows installation!"

1. In Settings open the 'Time & Language' section and go to the 'Region and Language' page.
2. Run Regedit (as an administrator) and rename HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate key to something else, e.g. WindowsUpdateXXX
3. Run services.msc from the search box and stop the 'Windows Update' service (right-click it)
4. Go back to 'Region and Language' and click your language (UK) and then the Options button
5. Download all the options: Basic Typing, Handwriting, Speech
6. Once downloaded, go to the 'Speech' page and you should see now be able to select your language there (UK)
7. Stop the 'Windows Update' Service again
8. Rename the registry key back to 'WindowsUpdate'
9. The WindowsUpdate service will restart itself eventually or you can start it if you like
10. Run Cortana and it should work, now that all your languages are the same (and supported)!

Problem Solved!

Actually I was using Mobile Hotspot to download.

Windows 10 does not allow us to download language packs over a metered connection unless you enable downloads over metered connections from Settings.

The language pack was downloaded when I connected my PC to a WiFi network.

Later I downloaded English (India) too. Cortana is working fine now.