One bibliography, different categories (use of keywords)

Question

I apologize whether my problem is too obvious, but I would like to know what I'm missing. My problem is: I used two type of keywords ("cited" and "Other"), in my .bib file, because I would like to get one Bibliography with two sections, where in the first one ("Main sources") I list all the references that I used in my work (with \cite), and in the second ("Seen") just those that I read, but not used in my work.

In the main I used

    \printbibliography[keyword={cited},heading=subbibliography, title= {Main sources}]
    \printbibliography[keyword={other},heading=subbibliography, title= {Seen}]`

But I know that resources with keyword "other" don't appear. I think I misunderstood the correct way of using .bib. Any Idea?

I also attach one MWE:

\documentclass[11pt,twoside, openright, cleardoublepage=empty
]{book}
\usepackage[english]{babel}
\usepackage{geometry}
%\geometry{a4paper,top=35mm,bottom=35mm,inner=30mm}
\usepackage{fancyhdr}
\pagestyle{fancy} 
\fancyhf{}
\usepackage{emptypage}
\fancyhead[RO]{\nouppercase\rightmark} 
\fancyhead[LE]{\textit\leftmark}
\fancyfoot[C]{\thepage}
\usepackage{blindtext}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage[font=small,format=hang,labelfont={sf,bf}]{caption}
\usepackage{graphicx}
\usepackage[colorinlistoftodos]{todonotes}
\usepackage{caption}
\usepackage[toc,page]{appendix}
\usepackage{titlesec}
\usepackage{floatrow}
\usepackage{siunitx}
\DeclareSIUnit \year {y}
\usepackage{eurosym}

\PassOptionsToPackage{hyphens}{url}\usepackage{hyperref}

\usepackage[
backend=biber,
style=authoryear,
citestyle=authoryear,
dashed=false,
sorting=nty,
firstinits,
minbibnames=6,
maxbibnames=8,
maxcitenames=2,
uniquelist=false
]{biblatex}


\addbibresource{References.bib}
\renewcommand*{\nameyeardelim}{\addcomma\space}
\renewcommand*{\finalnamedelim}{%
  \ifnumgreater{\value{liststop}}{10}{\finalandcomma}{}%
  \addspace\&\space}
\renewbibmacro{in:}{}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{document}
\frontmatter
\tableofcontents
\listoffigures
\listoftables

\mainmatter
\chapter*{Introduction}
\markboth{Introduction}{}
Lorem ipsum dolor sit amet,

\chapter{First}
\section{one}
\section{two}
\section{three}
One image
\begin{figure}[ht]
    \centering
    \includegraphics[scale=0.25]{example-image-c}
    \caption[Capital letter C]{This is capital letter C}
    \label{fig:my_label}
\end{figure}
and a table:
\begin{table}[ht]
    \centering
    \begin{tabular}{|c|c|}
\hline
1 & 2   \\ 
\hline
    \end{tabular}
\caption[1 and 2 data table]{This is a table with 1 and 2}
\label{Table}
\end{table}

Here I make one reference \cite{Spectralvelocities}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%% BIBLIOGRAPHY
\printbibheading
\printbibliography[keyword={cited},heading=subbibliography, title= {Main sources}]
\printbibliography[keyword={other},heading=subbibliography, title= {Seen}]

\addcontentsline{toc}{chapter}{Bibliography}

\end{document}

And the bib file:

@article{Spectralvelocities,
  title={Limiters for spectral propagation velocities in SWAN},
  author={Dietrich, J.C and Zijlema, M. and Allier, P.-E. and Holthuijsen, L.H. and Booij,N.},
  journal={Ocean Modelling},
  pages={85-102},
  year={2012},
  keywords={cited}
  }

%%%%%%%%%%%%%%%%%%%%%%%%%%
@manual{Deflt3D,
  title={Delft3D-WAVE User Manual},
  author={{Deltares}},
  edition={version 3.05.34160},
  publisher={Deltares},
  year={2014},
  keywords={other}
  }

@book{Sorensen,
  title={Basic Coastal Engineering},
  author={Sorensen, Robert},
  publisher={Springer},
  year={2006},
  edition={3},
  keywords={other}
  }