Description:
Environment is Clarity 12.0.6. The links "Forms", "Documents", "Action Items", "Discussions" and "Calendar" are all missing from screen display.
Solution:
The problem was caused by XDM not being deployed correctly. When the XDM was redeployed the collaboration functionality returned to normal.
From NSA-> Install and Upgrade-> XDM, do a Re-Install to redeploy XDM.