Hey, thanks for the report. Try pressing Ctrl+E. It toggles the layout between Editor and Agent mode. The “Review next file” button only shows up in one of the modes, and sometimes the layout gets switched by accident.
A few users have run into the same thing. Here’s the thread with details and screenshots: Next file button
If Ctrl+E doesn’t help, please share a screenshot of the editor top bar so we can see what state the UI is in right now.