Hello Ronaldo,
the statement looks fine. Thus please check the following things..
1. In the debugger, is IT_KEY filled with correct instances of the node?
2.Define the node and the association explicit via constant interface to ensure, that you have the right keys.
3. Check if the association you're using is correctly implemented or its binding correct maintained.
4. Ensure that there is a target instance available at all
Best regards
Tilmann