ngc digits could not plot the bboxinges for DetectNet.

I am using the digits from here,
with command:
nvidia-docker run -p 5500:5000 -v /home/vxgu/mnist:/mnt digits_caffe:19.09

I am running the detectnet for dog detector, like in

I can see the dog part in last two layers ,but the bbox-list did not output anything

what is the problem?