When a file is uploaded to Kaizena.com, Kaizena takes a "snapshot" of the file. Any subsequent changes to the file won't show up on Kaizena.com unless the file is added again. This lets you capture your students work at a particular time, and lets you see how the student responds to feedback.
Kaizena Shortcut makes it easy to add a revised version of a file to Kaizena.com. Open Kaizena Shortcut, then click "Get feedback on new changes":
A new version of the Google Doc will be added to the Conversation on Kaizena.com, and you will be taken to the Conversation.