Open the Collab toolbar and then click History, or select Window > Collab History to open the Collab History window.
This window shows the entire history of the project and any changes made. You can also “Go back to…” previous versions, or “Restore” to the most recent submission. Restore removes all of your local changes.
Is something described here not working as you expect it to? It might be a Known Issue. Please check with the Issue Tracker at issuetracker.unity3d.com.