You have directory message enabled for a Directory part in NetCommunity. When clicking to send the message to a member of the directory, you receive the following error message:
Subject line is required. Please enter a subject line.
This is typically the result of two directory parts on the same page. When only one directory part is on the page, the message works successfully. As a general practice, we recommend having only one directory part on a page because having two can lead to unexpected behaviors, similar to what we're seeing with an error.
Steps to Duplicate
Initiate a search in the directory part
Click the message icon next to the person you want to email
After customizing the subject and body, click Send