I have tried adding Inverse Kinematics to the legs of my humanoid model using this tutorial: https://www.youtube.com/watch?v=jp_SqjB0468
However, when I move the IK bone, the leg won't bend at the knee for some reason. I have checked the Parenting relationship between the Lower and Upper Leg and everything seems to be in order. How do I fix this so that the leg bends at the knee when I move the IK bone?
Here is a link to my .blend project: https://drive.google.com/file/d/1darEP59YbALtv4lqDqYXXS6K270zA3_n/view?usp=sharing