Solids: edges with 3 or more faces. How to fix

Hi. I have two concentric circles on the same plane. I extrude upwards to make a tube, triple click and make a group. SuSolid reports edges with 3 or more faces on the inner circle at the base of the extrusion so it is not a solid. How do I fix this?

Without an image or the model it’s a bit hard to know, but my guess would be that you haven’t deleted the face of the inner circle. So you have a tube that should be a solid but it has a single face on the end blocking the water flow so to speak.
If that is the case, just delete that face and it should be a solid.

Thanks very much, you have fixed my problem.