Hi Zhenlin,
The issue is with the preserves not going sick due to the mirror and body removals made in the Edit Model workspace. We should be marking the preserved bodies as missing to inform you that something isn't right. Since there are no longer any preserved bodies, it is causing the previewer to fail.
You can verify this by going to Edit Model and roll back the timeline marker (at least prior the last mirror and body removals) then roll it forward again. This will force a recompute. When you return to Define the study setup, you'll see that the preserves are now correctly marked as missing.
We have it logged in our system as ID-57946 and will forward it on to Development for further investigation.
You can repair the setup easily by editing the design space, and selecting the mirrored bodies for preserves and obstacles. The loads and constraints will find their lost targets automatically, once the preserve and obstacle associations are re-established.
Thank you for bringing this to our attention, and we apologize for the inconvenience this is causing.
Best regards,
Hugh Henderson
QA Engineer (Fusion Simulation)