Question
What does the message Take this ticket to join the conversation mean?
Answer
When agent collaboration for messaging is turned off, only the assigned agent can message the customer. To reply to the customer, click Take it in the Assignee field to automatically assign the ticket to yourself.
Select Submit as Open to apply the change to the ticket.
If you want to join the conversation, switch to Internal note from the composer and reply to the ticket.
For more information, see this article: Receiving and sending messages in the Zendesk Agent Workspace.