Activate the Approach

[Greaser]

On some flights I have activated the approach Ok, the IAF became the activate way point and the approach started.  However at other times, like just now, I have an approach in the system entered previously, but after pressing Menu, there is no such menu item to Activate the Approach.  I see Activate Leg, but not Activate the Approach. Any idea what I am doing wrong? 

Edited December 17, 2018 by Greaser

[RobW05]

The activate approach can be found under Proc, not Menu.