Hello community and sorry for my poor english.
It looks like at the 1st start Lifesize App doesn't allow to change the language. So, a guest or an unauthenticated Lifesize user have the interface in English by default. Once authenticated, a Lifesize user can change the language.
The request is to be able to access the "File / Settings / Audio, Video and Language Settings" window even if we aren't authenticated.