Submixes doesn't work!

Hi, I have a weird problem with this project (All other projects work perfect)
I can’t hear sounds and also I can’t call to submix classes. They look deactivated or something like that. I’m desperate

Also when I come into MasterSubmixDefaul only see the details but not the graph!

Another thing is that when I’m going to Sounds > Mix I CAN’T find this menu!