The command \newpage does not begin a new page in mcexam. I need the \begin{mcquestioninstruction} to begin on the next page because it is orphaned from the questions that follow.
Update: \newpage is now inserted after the \begin{mcquestioninstruction} line. This does put the instruction on the next page as desired.
\documentclass[a4paper]{article}
\usepackage[output=exam
,numberofversions=2
,version=1
,seed=1
,randomizequestions=false
,randomizeanswers=true
,writeRfile=true
]{mcexam}
\usepackage{tikz,framed}
\usepackage{fancyhdr,lastpage}
\usepackage{tcolorbox}
\tcbuselibrary{skins}
\usepackage{chemformula}
\usepackage{chemmacros}
\usepackage{graphicx}
\usepackage{enumitem}
\usepackage{array}
\graphicspath{ {./images/} }
\hyphenpenalty=2000
\pagestyle{fancy}
\fancyhf{}
\renewcommand{\headrulewidth}{0pt}
\renewcommand{\footrulewidth}{1pt}
\lfoot{\mctheversion}
\rfoot{Page \thepage\ of \pageref{LastPage}}
\usepackage{calc}
\renewenvironment{setmcquestion}{\begin{minipage}[t]{\linewidth-\labelwidth}}{\end{minipage}\par}
\begin{document}
\mcifoutput{concept,exam}
\section*{}
\begin{mcquestions}
\question Question 1
\begin{mcanswerslist}[fixlast]
\answer [correct] answer 1
\answer answer 2
\answer answer 3
\answer answer 4
\end{mcanswerslist}
\begin{mcquestioninstruction}
\newpage
My instructions that must be at the top of the next page:
\end{mcquestioninstruction}
\question Question 2
\begin{mcanswerslist}%[fixlast]
\answer answer 1
\answer answer 2
\answer answer 3
\answer answer 4
\end{mcanswerslist}
\end{mcquestions}
\end{document}

\newpageis on a new page, hard to understand as you describe it asorphanedfrom the questions that follow. Moving\newpagewithin\begin{mcquestioninstruction}creates a new page but Question 2 is on it too, could you clarify please – JamesT Jun 21 '23 at 20:06\begin{mcquestioninstruction}. Your solution achieved what I needed. – larryjb Jun 21 '23 at 21:46