Head to the 'Issue Tracking' tab under the 'Building Management' icon.
Select the ticket to which you would like to reply to.
Scroll down to the comment section.
Type in your message and check the 'Post for Client' box before sending so that the resident can view your message.
The comment section also shows ticket information such as the ticket being create, started, when a schedule is set and completed.
*Note: Tickets that have been are been last updated/interacted will have a green dot next to them as shown in the image above. This will appear every time a residents leaves a new comment.

