Hi, N.K04.
Welcome to the Microsoft support community.
I noticed that you are trying to restore the language you are missing. But the situation you describe is pretty weird for me, so I have to ask:
1 When you say your language list are now become empty, what does your language list look like when you try to open the Setting > Time & Language > Windows display language?
2. What action have you done before you does not see any language list anymore if you could recall?
3. Is the add normal add language option not work anymore, any error message when you trying to do that?
--------------------------
For your question:
1) There are no offline language pack available for download for Windows 10 and Windows 11 anymore.
2) Without your detail information I am afraid I cannot determine what kind of cause of your language issue is. But it is a good habit to keep a restore point of your system.
3) You might try if your system can went back to normal mode by entering the safe mode:
1-> Press Windows logo key + I on your keyboard to open Settings. If that doesn't work, select the Start button, then select Settings . 2-> Select Update & Security > Recovery .
Open Recovery Settings 3-> Under Advanced startup, select Restart now. 4-> After your PC restarts to the Choose an option screen, select Troubleshoot > Advanced options > Startup Settings > Restart. You may be asked to enter your BitLocker recovery key. 
5-> After your PC restarts, you'll see a list of options. Select 4 or press F4 to start your PC in Safe Mode. Or if you'll need to use the internet, select 5 or press F5 for Safe Mode with Networking. |
Let us hope your problem will get solved soon, looking forward about your reply.
Best Regards
Benjamin- MSFT | Microsoft Community Support Specialist
