i used to have my iMac i3 in french, and now the language is lock in english

Hi,

You can try to open "Terminal" App,

Enter

sudo languagesetup

"Press enter"

Enter your Admin password and then "Press enter" (You won't see your password and it's normal)

Then choose your language > you'll have a list of languages with numbers > just look for french (number two I Think)

"Press 2, and Enter"

Then restart you Mac and see

Otherwise :

You will have to make a back up first

Use Time Machine to back up or restore your Mac - Apple Support

And then Reinstall macOS :

How to reinstall macOS - Apple Support

> Start with Mac with Cmd+R pressed and then click on "Reinstall macOS".

This manipulation won't erase your datas.

Hi,

You already reinstall the OS ?

You can try as well :

1- Run Malwarebytes and see if a malware can be the issue

https://www.malwarebytes.com/mac/

2- Start in Safemode and see if you can change the language

Use safe mode to isolate issues with your Mac - Apple Support

3- Create a Test User session and see if the same issue happen

macOS Sierra: Set up users, guests, and groups on your Mac

If nothing worked, I guess you'll have to erase your disk and reinstall the whole system.

macOS Sierra: Erase and reinstall macOS

Make sure to have a TM back up first 😉