LaTeX Error: Something's wrong--perhaps a missing \item, but the item is there

Question

I'm trying to write a list in an enumerate environment, but for some reason even if the code is (apparently) correct, Latex gives me the following error at the second line: "! LaTeX Error: Something's wrong--perhaps a missing \item."

Point is, this the code;

\begin{enumerate}
    \item La soluzione per $\theta$ da' la conferma che il moto si svolge su un piano;
    \item La soluzione per $\phi$ restituisce la conservazione della velocità aerolare;
    \item La soluzione per r è la nota equazione dell'ellisse.
\end{enumerate}

And it follows the rules that I've seen on basically every LaTeX manuals on the internet, this "missing \item" is clearly there. I also have already the \usepackage{enumitem} activated, I'd say is also pretty standard. Someone might say that I could just skip it, the problem is that if I compile the code, this is the only error I get; If I delete this whole part of the code, the same error shows up on the following "itemize" or "enumerate" environment and so on, and that basically would mean that I should get ride of every list of the document to make it work, which is not exactly doable in a thesis. Maybe the solution is pretty dumb, but really I can't wrap my head around it. Thank you in advance.

EDIT: Ok, following your advices I tried to find the specific lines that are the sources of the problem and this is what I got

\begin{figure}[h]
\includegraphics[scale=0.5]{Potenziale.png} 
\caption{potenziale}
\flushleft
\end{figure}
\clearpage
\newpage
\begin{enumerate}
    \item La soluzione per $\theta$ da' la conferma che il moto si svolge su un piano;
    \item La soluzione per $\phi$ restituisce la conservazione della velocità aerolare;
    \item La soluzione per r è la nota equazione dell'ellisse.
\end{enumerate}
\end{document}

Normally, between the \newpage command and the part that I wrote before there are something like 200 lines of code. Clearly you don't have the source image so I suppose the code can't be ported somewhere else, but this is the situation. I tried to delete the image linked and it works; I can go on without the pic anyway, so at least the problem is solved (though i'm still curious why an image in a totally different part of the document would resulte in a "missing \item" )

Answer 1

The \flushleft is an error, because it is actually an artifact of the flushleft environment, which encloses ragged-right text set off from the running text with vertical spaces (at begin and end). If you want a command version, the command is \raggedright. (I presume it should go before the \includegraphics.)

How does it interact with \item? The flushleft definition uses a "trivial list" to get the vertical spacing of lists.

(This answer comes after the question was editied with revealing information.)

Answer 2

This works with me. (I changed the accents though)

\documentclass{report}
\begin{document}
\begin{enumerate}
\item La soluzione per $\theta$ da' la conferma che il moto si svolge su un piano;
\item La soluzione per $\phi$ restituisce la conservazione della velocit\`a aerolare;
\item La soluzione per r \`e la nota equazione dell'ellisse.
\end{enumerate}
\end{document}

in "standalone":

\documentclass{standalone}
\begin{document}
    \begin{minipage}{12cm}
        \begin{enumerate}
            \item La soluzione per $\theta$ da' la conferma che il moto si svolge su un piano;
            \item La soluzione per $\phi$ restituisce la conservazione della velocit\`a aerolare;
            \item La soluzione per r \`e la nota equazione dell'ellisse.
        \end{enumerate}
    \end{minipage}
\end{document}