Inactive Vassals

[Lagassy]

Hello! I want to know why my vassals are inactive?

I conquered a fort (so I were a king) and I have given one of my companion a fief. After that my Vassal just stayed in my fort, and did nothing.
Then I turned on the cheat mode, and conquered 2 fort, and I gave 1 fort and 1 village to one of my companion, and nothing happened... My vassal just stayed in the fort and did nothing. And this is the problem again and again. What should I do?