Why hasn't the movie plea of innocence been released yet?

The film "Plead of Innocence" is based on Zhang Biao, a retired prosecutor of Shihezi People's Procuratorate. Based on the "rape death case" of Zhang Gaoping and Zhang Hui in Zhejiang Province, this paper reproduces the story that prosecutor Zhang Biao found suspicious points in the process of law enforcement and finally avenged Zhang Gaoping and Zhang Hui's uncle for five years.