# breakable in tcolorbox not breaking

\documentclass[12pt, a4paper, UTF8, scheme = plain, twoside]{ctexart}
\usepackage{amsmath}
\usepackage{enumerate}
\renewcommand{\labelenumi} {(\roman{enumi})}
\renewcommand{\labelenumii}{(\alph{enumii})}
\usepackage[top=0.5cm,left=0.5cm,right=0.5cm,bottom=2.28cm]{geometry}
\usepackage{hyperref}
\usepackage{graphicx}
\pdfsuppressptexinfo=-1
\usepackage{lipsum}
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%%       - Fancyhdr -    %%
%%%%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage{fancyhdr}
\usepackage{totpages}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage{tcolorbox}
\tcbuselibrary{skins,xparse,breakable}
\tcbset{%
colback      = white,
tikz         = {opacity=0.1,transparency group},
colframe     = black,
title filled = false,
colbacktitle = white,
}%%
\NewTColorBox[
]{question}{ O{}mo }{
fonttitle                 = \bfseries,
coltitle                  =  black,
title                     = #2,
#1
}%
%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%
%%%  DOC Begins   %%%
%%%%%%%%%%%%%%%%%%%%%
\begin{document}
\thispagestyle{empty}
\begin{question}
% \lipsum[4]
Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah
\tcblower
$\lambda = 2\times10^5 \qquad l_0 = 2$
% \lipsum[4]
Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah Blah \lipsum[4-10]
\end{question}
%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%
\end{document}
%%%%%%%%%%%%%%%%%%%%%%%%%%%


Why does the breakable not working in this case?

• it is not enough to load the library, you must also use it. Check the documentation. Apr 5 at 9:55
• You load breakable library but the box (question) is not declared to be breakable. You have to include breakable in question options. Apr 5 at 9:55

As said in comments, you should not just load breakable, you must tell the box if it is allowed to be breakable.

I commented the tikz = {opacity=0.1,transparency group} to make your example visible and I also added the {Title} to your {question} environment. As you created a \NewTColorBox with two arguments, the first optional but the second doesn't seem to be ({question}{ O{}mo } and title = #2,).

A MWE follows.

\documentclass[12pt, a4paper, UTF8, scheme = plain, twoside]{ctexart}
\usepackage{amsmath}
\usepackage{enumerate}
\renewcommand{\labelenumi} {(\roman{enumi})}
\renewcommand{\labelenumii}{(\alph{enumii})}
\usepackage[top=0.5cm,left=0.5cm,right=0.5cm,bottom=2.28cm]{geometry}
\usepackage{hyperref}
\usepackage{graphicx}
\pdfsuppressptexinfo=-1
\usepackage{lipsum}
\usepackage{tcolorbox}
\tcbuselibrary{skins,xparse,breakable}
\tcbset{%
colback      = white,
%tikz         = {opacity=0.1,transparency group},
colframe     = black,
title filled = false,
colbacktitle = white,
breakable
}
\NewTColorBox[
]{question}{ O{}mo }{
fonttitle    = \bfseries,
coltitle     =  black,
title        = #2,
$\lambda = 2\times10^5 \qquad l_0 = 2$