Message field not showing in OJS

Description of issue or problem I’m having:
The massage field in discussion not showing, only appears ‘subject’ body.

Steps I took leading up to the issue:

What I tried to resolve the issue:
I have opened error_log, but found nothing about this error.

Application Version - e.g., OJS 3.1.2:
The system is on OJS

Additional information, such as screenshots and error log messages if applicable: