"deepstream-lpr-app 1 1 0 LPR.mp4 out.h264" gives "One element could not be created. Exiting."

Using Jetson nano (4GB) running jetson-nano-jp451-sd-card-image using NGC nvcr.io/nvidia/deepstream-l4t:5.1-21.02-samples.

I prepared the model elsewhere, without issue.

Using the above container, added the following software:

apt-get -y update
apt-get -y install tree make g++
apt-get -y install libssl1.0.0 libgstreamer1.0-0 libgstreamer1.0-dev gstreamer1.0-tools
gstreamer1.0-plugins-good gstreamer1.0-plugins-bad gstreamer1.0-plugins-ugly
libgstreamer-plugins-base1.0-dev gstreamer1.0-libav libgstrtspserver-1.0-0
libjansson4=2.11-1

After that I could “make” the application.

Created dict.txt for US plates, per directions.

File “us_car_test2.mp4” is missing from GitHub repo, so I made my own short video (called “LPR.mp4”).

Ran:

./deepstream-lpr-app 1 1 0 LPR.mp4 out.h264
One element could not be created. Exiting.

Looked through similar problems, found a hint about missing element “nvinfer”. Ran:

gst-inspect-1.0 nvinfer
No such element or plugin ‘nvinfer’

Where/how might I get this gadget?

Seems the JetPack4.5.1 is not installed correctly. Please check it or reinstall it.