Sometimes the File Changes button in the top right will be grayed out when you are in a workspace:
The issue can persist through creating a workspace or starting an existing one.
The issue can be caused by stale browser cache, or inactivity within the browser session.
This can be resolved by clearing the cache of your browser. If that does not work, log out of all of your open Domino sessions and close all Domino tabs, then log back into Domino.
If the issue is still not resolved, please contact Domino Support for assistance.