# Pgfplots label not appearing

\documentclass{article}
\usepackage{tikz}
\usepackage{pgfplots}
\usepackage{tkz-euclide}
\begin{document}
\begin{tikzpicture}
\begin{axis}[ticks=none,
xtick={-10,-9,...,10},
xmin=-6,
xmax=6,
xlabel={$\alpha$},
axis x line=middle,
ytick={-10,-9,...,10},
ymin=0,
ymax=10,
ylabel={$s$},
axis y line=middle,
no markers,
samples=100,
domain=-10:10,
restrict y to domain=-20:20, xscale=1.2 ]
\addplot[red,samples=400, domain=-1:1] (x,{-4*x/(1+x)^2}) node[pos=0.5, pin=135:{$\frac{-4\alpha}{(1+\alpha^2)}$}] {};
\draw[cyan] (axis cs:1,0) -- (axis cs: 1,10) node[pos=1, pin = -30: {\tiny $\alpha=1$}] {};
\draw[cyan] (axis cs:-1,0) -- (axis cs: -1,10) node[pos=0.5, pin = -120: {\tiny $\alpha=-1$}] {};
\end{axis}
\end{tikzpicture}
\end{document}


My one plot label \addplot[red,samples=400, domain=-1:1] (x,{-4*x/(1+x)^2}) node[pos=0.5, pin=135:{$\frac{-4\alpha}{(1+\alpha^2)}$}] {}; doesn't want to display for some reason. Does anyone see a problem with my code?

The label is outside of the axis rectangle, so it is cliped away. You can add an option clip=false, to the axis environment, but that would "unclip" the plots of your functions, which probably isn't what you want. Another option would be moving the red label so it is comnpletely inside of the axis rectangle.