Texshop / bibtex errors in docs that used to work

Question

I'm running Mac OS 10.13.1 (High Sierra) and Texshop Version 3.89. I opened Texshop for the first time in about 4 months today, and started to work on a document. I use Zotero to generate my BibTex file, also as usual. But I keep getting the following error:

This is BibTeX, Version 0.99d (TeX Live 2015)
The top-level auxiliary file: My_Paper.aux
I found no \citation commands---while reading file My_Paper.aux
I found no \bibdata command---while reading file My_Paper.aux
I found no \bibstyle command---while reading file My_Paper.aux
(There were 3 error messages)

I thought I was doing something wrong because I was rusty, so I went back to a paper I wrote 2 years ago that definitely worked. There, I saved the .tex, .cls, .bib, and .pdf files, but when I ran the .tex file, I got the same error.

Is this a problem with TexShop under High Sierra, or is there something else I have to update to get these old papers to run?

As a minimum working example, this .tex file works in Overleaf, but gives me the error above in Texshop:

\documentclass[letterpaper,12pt]{article}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{lmodern}
\usepackage{setspace}
\doublespacing

\usepackage[english]{babel}
\usepackage{csquotes}

\usepackage[notes,backend=biber]{biblatex-chicago}
\bibliography{paperbib}


\begin{document}
\title{Academic Paper:\protect\\With a Subtitle}
\author{Joan Q. Public}
\maketitle

Blah blah blah. 

Blah blah Einstein's Theory\autocite{einstein} which predicted blah.

The New York Times\footcite{nyt} reported blah blah. 

\printbibliography

\end{document}

Thanks in advance for any insight!