Great, then you will need to extract the flow volume from your model in CAD mode:
Then you will have to delete the body because, for the compressible analysis type, only the flow region must be used. Otherwise, the simulation will not start.
Then replace the geometry in your simulation, and assign the boundary conditions accordingly.
Keep in mind that our solver works well up to Mach ~ 0.7, so maybe you want to consider lowering the velocity if you can not achieve successful results with good meshes.
Also, you can use my project for reference, or just copy it: https://www.simscale.com/workbench/?pid=2104907080004406265&mi=spec%3Af541c2dd-604e-4bc1-a170-87ab7494d945%2Cservice%3AMESHING%2Cstrategy%3A9&sh=2
Best regards,
Fillia