Hi,
Please try the steps to make sure the camera source is good:
Jetson Nano FAQ
Q: I have a USB camera. How can I launch it on Jetson Nano?
And the latest release is for Jetpack 4.5:
Release Support JetPack 4.5 · NVIDIA-AI-IOT/jetbot · GitHub
Please use Jetpack 4.5 and try the package.