Thanks for your reply but the load is successful because the other strings are translated, only the one passing through QT_TR_NOOP and later tr() remain in English.
It is not English translation works and other don't, but the soft is made in English, and there is no problem with english messages, but when i want to translate it to another langage there is a problem.

But the problem has just been solved thanks to a friend.
I have to make my class inherit from QOBJECT, use the Q_OBJECT macro, and do not use QObject::tr() but tr() to be in the right context.