How can you reply to a completed email that was completed by someone else?

I’m helping an agent - When doing an advanced search for a completed case, he wants to reply to it, but eGain is only bringing up the original email from the customer and not the most recent current string of back and forth responses. (Does that make sense?) How do you reply to the most recent response? It’s all greyed out?

Hi Corina,
The case should show all the back and forth as activities. Does the agent (or his supervisor) see the same when searched on an admin account?

Regarding agent not being able to reply to completed emails, does the agent have the action to “Create Activity” in their permissions?

Is it possible to attach a screenshot for reference?