Check the attached fix.
You Sculpted the surface bodies into a second solid body for the Combine-Subtract.
Inventor sheet metal does not support multi-body solids - thus the error.
I deleted your Sculpt and deleted the extra surface faces you had. (When Copy Object to get the surface - you only need the outer contact surface).
Now I used Sculpt (or Split) to cut away the excess without creating an solid bodies).
Log into access your profile, ask and answer questions, share ideas and more. Haven't signed up yet? Register