It's helpful if you can list all of the mods you're running when having this problem. As Wilde said, if you're running AGM on it's own and the 506th pack it may be conflicting and bugging out. This is all you need to have running as mods in order to take part in missions.
@CBA_A3
@506th
@AllInArmaTerrainPack
@RHSAFRF
@RHSUSF
@task_force_radio
The 506th Pack itself has a bunch of mods already packed inside it, a custom setup of AGM being one of them. As I understand it, any other mods are not allowed by command and may also conflict with the 506th pack.