When you select a different language and it is not activated, it usually happens that the marks disappear.
You should contact your vendor and provide the serial number of your equipment, and request that you activate the language you need. When they confirm that it is already activated go to CONFIGURATION - LANGUAGE - you select the language and you will get a message that tells you that you must update, you return to the main menu and you go to UPDATES, and that's it.
Regards