My company recently migrated to cloud. We've been accustomed to using the [capslock] J and K keys to navigate through the list of files in a pull request. The documentation indicates that this should still work, but it hasn't, either in the legacy PR layout or the new Labs tabbed layout.
I have keyboard shortcuts enabled in Personal Account Settings. I've also tried using the keys with various parts of the page in focus, such as the sidebar list, the active file view, etc.
In a remarkable coincidence a similar query was posted under Questions just now.