About Isaac sim for automous dirving simluation

[ZhengDonglei]

Dear officer:
I m starting to build a simlation environment and learn from the ISAAC SIM documents for some times. But when I create my own automous driving simulation, I found that the Car can t move on the ground I imported from the URDZ file, however it can run on the default groundplane, it makes me struggle. My question is have you meet this situation before? Or the are any setting needed when import the groundplane file?
Besides, where did you learn how to use the ISAAC SIM? It seems that there are few turtorial on the Internet.
Best regards.