Error using subfloat and centerline in figure

This may point you in correct direction

documentclass[demo]{article} % remove 'demo' option in real document
usepackage{graphicx,subcaption}
begin{document}
begin{figure}[!htb]
captionsetup[subfigure]{font=bf}
begin{subfigure}{0.16linewidth}
includegraphics[width=1textwidth]{420}
caption*{420}
end{subfigure}hfill
begin{subfigure}{0.16linewidth}
includegraphics[width=1textwidth]{421}
caption*{421}
end{subfigure}hfill
begin{subfigure}{0.16linewidth}
includegraphics[width=1textwidth]{422}
caption*{422}
end{subfigure}hfill
begin{subfigure}{0.16linewidth}
includegraphics[width=1textwidth]{423}
caption*{423}
end{subfigure}hfill
begin{subfigure}{0.16linewidth}
includegraphics[width=1textwidth]{424}
caption*{424}
end{subfigure}hfill
begin{subfigure}{0.16linewidth}
includegraphics[width=1textwidth]{425}
caption*{425}
end{subfigure}
end{figure}%
begin{figure}[!htb]
    captionsetup[subfigure]{font=bf}
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{420}
        caption*{420}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{421}
        caption*{421}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{422}
        caption*{422}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{423}
        caption*{423}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{424}
        caption*{424}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{425}
        caption*{425}
    end{subfigure}
end{figure}%
begin{figure}[!htb]
    captionsetup[subfigure]{font=bf}
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{420}
        caption*{420}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{421}
        caption*{421}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{422}
        caption*{422}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{423}
        caption*{423}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{424}
        caption*{424}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{425}
        caption*{425}
    end{subfigure}
end{figure}%
begin{figure}[!htb]
    captionsetup[subfigure]{font=bf}
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{420}
        caption*{420}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{421}
        caption*{421}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{422}
        caption*{422}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{423}
        caption*{423}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{424}
        caption*{424}
    end{subfigure}hfill
    begin{subfigure}{0.16linewidth}
        includegraphics[width=1textwidth]{425}
        caption*{425}
    end{subfigure}
end{figure}
end{document}

After half of year ... Since your main problem is solved by @P.M. comment, here are some off-topic suggestion how you can correct/improve your MWE:

• because all images has the same width, you can use common settings for it by setkeys{Gin}{...}
• for centering of images on page is better than centerline{...} to use command centering
• for starting new row of images just insert empty
• instead of fix distance between image used hfil

documentclass{article}
usepackage{graphicx}
usepackage{subfig}

%---------------- show page layout. don't use in a real document!
usepackage{showframe}
renewcommandShowFrameLinethickness{0.15pt}
renewcommand*ShowFrameColor{color{red}}
%---------------------------------------------------------------%
begin{document}
begin{figure}[htb]
centering
setkeys{Gin}{width=13mm}
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}

    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}

    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}

    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}hfil%
    subfloat{includegraphics{example-image}}
caption{caption}
    label{fig: Sos Prediction}
end{figure}
end{document}