Encoding problem with accents and inputenc package

I have this problem, it seems I'm doing something wrong while writing letters with accents like è, on that line the compiler says: package inputenc Error: unicode char \u8:èun not set up for use. This happens when I use my LaTeX editor, compiling the same code with an R sweave file on Rstudio it works normally and I got my accents on letters.

The code used is:

\documentclass[12pt,a4paper,oneside,openright]{book} %oneside versione segreteria \usepackage[a4paper,top=2cm,bottom=2cm,left=3cm,right=2.5cm]{geometry} \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \usepackage[english,italian]{babel} \usepackage{bm} \usepackage{amsmath} \usepackage{mathrsfs} %\uspackage{graphicx} \usepackage{hyperref} \begin{document} %________________________________________________________________ \frontmatter %space for abstract \pagestyle{plain} \tableofcontents %_______________________________________________ \mainmatter \pagestyle{plain} %Primo Capitolo %\addcontentsline{toc}{chapter}{Introduzione} \chapter*{Introduzione} L'accrescimento è \end{document}