Can you also please try the Isaac Sim 2021.2.0 release?
There were a variety of fixes from the PhysX team merged in.
https://docs.omniverse.nvidia.com/app_isaacsim/app_isaacsim/install_basic.html
see the known issue for downloading assets
https://forums.developer.nvidia.com/t/known-issue-assets-not-downloading/196122/2
And a link to a new set of tutorials which might be helpful in answering general questions
https://docs.omniverse.nvidia.com/app_isaacsim/app_isaacsim/tutorial_required_interface.html