Green bar not showing for favorites in FCPX

MacBook Pro, 1tb, 16Gb RAM.

IOS 10.9.4

Final Cut Pro 10.1.3 Trial Version.

Just started using FCPX demo, so I'm a newbie. Just diving into my first video using this. I seem to have lost the green bars which appeared during my practice sessions (thanks Izzy)...any ideas. The orange bars which denote a clip has been used in the timeline is there but I can't, for the life of me, get the green strip to appear either by pressing the start or F button.

Tx,

Mark