Microsoft recently pushed out a new preview of Windows 10 (build 10041) and while the company announced that Cortana is now available in more countries, including China, UK, France, Italy, Germany and Spain, many users are reporting issues enabling Cortana in the newly added languages.
Previously, people were just able to change the language, clock and region settings to English (United States) to get Microsoft’s digital assistant working, but it’s not the case anymore beginning with Windows 10 10041. Now to enable Cortana, you must install first the operating system in one of the supported languages (United States, China, UK, France, Italy, Germany or Spain).
If you’re not running one of the supported versions of Windows 10 to enable Cortana, Microsoft recommends to go to the Windows Insider web page and download the latest ISO for Windows 10 (build 9926). If you get an error trying to access the ISO files, go to the Windows Insider program site, sign-in with your credentials, click the “Before you install” link from the menu, scroll down, click “Get the preview”, from the instructions, click the “download the ISO files”, and the proceed by downloading the correct language of Windows 10.
At this time, you can only download build 9926, you can either get this version, or you can wait until Microsoft releases the ISO files for Windows 10 build 10041, once the company pushes the new build to the Slow ring. Though, you can create your own ISO installation media with these instructions.
Make a clean install of the operating system, change the Windows Update settings to the Fast ring to get build 10041 and proceed with the installation. After installing the operating system correctly, you’ll be able to use Cortana in the desktop.
If you decide to keep your previous settings moving to the new build, make sure to do the following: Go to Settings / Time & Language / Region & Language. Check the Country or region setting and check the Windows display language (set as default) setting.
Then go to Settings / System / Speech, and check the Spoken language setting.
Source Microsoft forums