@Resonance VEN (27 May, 2015, 4:37 AM UTC):
For the field kitchens, you need to upgrade all your field kitchens currently existing to level 20, before you can build another.
As for the Landing Zones, I think this is a possible bug similar to Total Domination: Nuclear Strategy, where they were over lapped.
To fix the field kitchens, simply upgrade them all before you build another.
To fix the Landing Zones, go into the base layout edit mode, then move around your Landing Zones until you see the sixth.