I've not played this one in a while but the likely answer is that the enemy are in dead ground. So even though they are within your units designated arcs of fire they cannot be seen by teams with the weapons systems to kill them.
Right click on the unit you want to fire, and select the "info" menu item. If there is a red line to the enemy vehicle, it will fire. Otherwise, it cannot positively identify the enemy and will not fire, unless given the suppress order.
Red lines to the vehicle from both Abrams and Bradley.
As stated in my first post I was not allowed to attach save games (as asg. files). How do I do that?