LaTeX Image Not Showing or Not Found
If \includegraphics shows nothing or errors with "file not found", check three things: load \usepackage{graphicx}; use a supported format (PDF, PNG, or JPG for pdfLaTeX — not EPS directly); and give the correct name without the extension, with the file uploaded to your project. Add \graphicspath{{figures/}} if images live in a subfolder.
Why it happens
pdfLaTeX only embeds PDF, PNG, and JPG. An EPS file, a wrong filename, a missing graphicx package, or a file that is not in the compile directory all make the image fail — sometimes silently, sometimes as "File not found" or "Cannot determine size of graphic".
Example
\usepackage{graphicx}
\graphicspath{{figures/}} % optional subfolder
\begin{figure}[H]
\centering
\includegraphics[width=.6\textwidth]{plot} % no .png needed
\caption{...}
\end{figure}
% EPS image? Convert it to PDF, or add \usepackage{epstopdf},
% or compile with XeLaTeX / LuaLaTeX.Frequently asked questions
It says "Cannot determine size of graphic".
Usually a wrong format (e.g. EPS with pdfLaTeX) or a corrupt file. Convert the image to PDF/PNG/JPG, or add \usepackage{epstopdf} if you must keep EPS.
Do I include the file extension?
Best not to: write \includegraphics{plot} and LaTeX picks the right file. If you have both plot.png and plot.pdf, then add the extension to disambiguate.
The image is in a subfolder.
Set \graphicspath{{figures/}} (note the double braces and trailing slash), or reference it inline: \includegraphics{figures/plot}.
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