need help in auto train

[pokezero]

as in castle fight the unit is auto trained and when i want to upgrade the structure i normally turn off the production of unit and select to upgrade the structure but ....when i do this (in my map i want to create) i found that the upgraded structure wont auto train my unit why? plz help

 

[Bribe]

Is it auto-training in a trigger? Does your upgrading building have that unit on its list of "units sold"?