cleveref package produces “??” [closed]

Question

I've used the second answer in Multiple references to the same footnote with hyperref support - is there a better solution?, yet, like @Jake in the comments, it produces some ?? in my document. Anyone has a clue?

Edit 1: I've compiled twice. The code is exactly the one of the second answer (shown below). And I got something like First page, referencing future footnote?? 2. in the pdf.

\documentclass{article}
\usepackage{hyperref}
\usepackage{cleveref}

\crefformat{footnote}{#2\footnotemark[#1]#3}

\begin{document}
First page, referencing future footnote\cref{second}.

Second paragraph, first footnote\footnote{\label{first}First footnote!}

\pagebreak
Second page, creating the second footnote\footnote{\label{second}Second footnote}, and referencing the first footnote\cref{first}.
\end{document}

Edit 2: Problem solved. Please help close the question, thanks.