It might be due to your graphics not meeting ANSYS Discovery Live Graphics Requirements.
Make sure your GPU meets the recommended hardware requirements (8GB GPU RAM)
Try running with a higher fidelity setting and/or with a larger GPU.
Try to reduce the simulation bounds by removing some parts of the model.
Last resort: Try increasing the feature size by thickening the walls, etc.
You can check ANSYS Discovery Hardware Requirements through below post:
Ansys Discovery Hardware Requirements (2022 R2)