When I write something in G clef 8 down, dorico don’t show the octave down reproduction and still play the notes as if I writed it in normal G clef. How can I fix it? I use Dorico Elements.
You need to set Notation Options > Clef settings to “Respect ottava clefs”. Or select a given clef and in the Properties panel, change the Octave Shift for that clef.
The Notation Option definitely won’t be available in Elements. I’m not sure about that property, though.
As pianoleo says, Notation Options isn’t available in Elements and the other option you say, I think it not works as I want. When I access on clef’s property panel, I can change the octave shift but it rewrites the music an octave up or down and what I want is an octave change when playback. Any idea?
Select the notes and change the pitch by an octave with the Ctrl-Alt-Up or Down arrow shortcuts.
Changing the clef does not change the pitch of existing notes. (It would be crazy if you wrote middle C in the treble clef, then changed to the bass clef, and the middle C turned into a low E below the staff!)
No: it doesn’t rewrite the music. The music stays where it is. The clef moves! 
What benwiggy said is fundamental to understanding how Dorico works in general, not just in this particular instance.
Dorico “knows about” the semantics of what the notation means, not just how it appears on the page. For example a “note” has a pitch and a duration. Those properties don’t change, but its appearance can change depending on the context.
For example if you have an F (natural) and you then add a key signature with sharps earlier in the score, that note will now have a natural sign which it didn’t have before. It doesn’t “change from F natural to F sharp.” If you change the time signature, a single written note might be visually split into two notes tied together either side of a bar line, but Dorico still “knows” it is really one long note. If you change a clef or add an 8va line , the note is now drawn in a different place on the staff but still has the same sounding pitch. And so on…
Sorry to both. I know what you are explaining me, english is not my language and I expressed myself wrongly. By the way, I solved the problem using the concert and transposition pitch. Now, when I work in transposition pitch, I have the notes in the pitch that I want and when switch to concert pitch, the notes move to the “real” octave. What I want is solved, I can work in transposition pitch but hear the playback on real octave.
I use Google Translate when I think I can contribute to a post in a language other than English. If you think you can explain better in your own language, you can do what a number of others have done and send your message in your native tongue and let the rest of us adjust.
Thanks! I will do it.