I can not make a fillet on a polysurface

I can not make a fillet on a polysurface.

coperta 46 .3dm (119.6 KB)

Hi Giuseppe . Apparently there are no problems with the fillet. What command have you used?
fillet ScreenFlow.mp4 (7.4 MB)

I used to fillet surfaces, because it does not work?
Thank you Zsimon

Your object is a solid, the fillet surfaces is not working. Eventually you have to pull the surfaces to be joined and work with those.