What age were you in when you researched all those techs? - If you are in say feudal you cannot research an imperial tech or castle techs for that matter, you can only research techs which you can research anyway legally.
By the way, if you are in imperial you dont need to research the whole line of techs for that unit or armour, just the one you need, and all the prior techs will be researched at the same time.
By the way you have to make sure that the trigger starting state is on, or if off make sure that another trigger activates the trigger.
[This message has been edited by Guderian (edited 01-13-2001).]