By the parent BP you mean BP_Unit and by child BP is BPA_Damageable?
Tag and Interface are specified in BP_Unit(for Particle, for a test) and in BPA_Damageable(Widget). In BP_Unit work all good, but in BPA_Damageable with the same code i can’t get a Print String.
It looks as if everything inside the BPC_Damageabale(3 image) does not see. Perhaps need to adress the component and not to the actor