This is probably because you did not name the node as specified. Did you check out the things Gradebot asked you to? Here is what it said:
To check the name of the node subscribed to /odom,
# launch your quiz in one terminal
ros2 launch topics_quiz topics_quiz.launch.py
And
# Check the subscriptions to `/odom` in another terminal
ros2 topic info /odom -v
If needed, you can share the output here.
You can refer to a similar case here: