Users are unable to use talk pages on pages such as this:
https://pt.wikibooks.org/wiki/Utilizador:Raylton_P._Sousa/Projetos/Livro_aberto
The talk page link points to
https://pt.wikibooks.org/wiki/Utilizador_Discuss%C3%A3o:Raylton_P._Sousa/Projetos/Livro_aberto
which says "The requested topic does not exist."
See also