problems using apa6e with biblatex-apa

The problem with your sample document is that you are missing the line

\DeclareLanguageMapping{american}{american-apa}

This should appear after you have loaded biblatex.

If you are still having problems with your sample document, the following sample document works correctly with a standard MacTeX/TeXShop setup. (Although I was able to get your example to work.) Try this and see if it works for you. The {filecontents} environment is just a way of including a specific bib file within the source document. You wouldn't need it for your actual document.

\documentclass[endnotes]{apa6e}
\usepackage[american]{babel}
\usepackage{csquotes} 
\usepackage[style=apa]{biblatex} 
\DeclareLanguageMapping{american}{american-apa}
\usepackage[T1]{fontenc}
\title{A title}
\author{An Author}
\shorttitle{A title}
\authornote{}
\abstract{An abstract}

\begin{filecontents}{apa-test-bib.bib}
@book{Saussure1995,
    Author = {Ferdinand de Saussure},
    Origyear = {1916},
    Publisher = {Payot},
    Title = {Cours de Linguistique G{\'e}n{\'e}rale},
    Year = {1995}}

@book{Labov1972,
    Address = {Philadelphia},
    Author = {William Labov},
    Publisher = {University of Pennsylvania Press},
    Title = {Sociolinguistic Patterns},
    Year = {1972}}

\end{filecontents}
\addbibresource{apa-test-bib.bib}

\begin{document}
\maketitle

This is some text. \cite{Saussure1995,Labov1972}
\printbibliography
\end{document}