Cant Import Dynamo Solid into Revit

Hi ,
i need some help creating a solid body in dynamo and export it to revit.
Sadly i cannot upload my dynamo file so i try to explain what i do.
I created a new Family via the conceptual mass template , after that i create a body in dynamo by using some points to a polygon and Solid.ByLoft and ImportInstance.ByGeometry. All works fine but if i load the family in another project i get the message : Mass contains only mesh geometry, which can’t be used to compute Mass Floors, volume, or surface area.
And i cant use it as the other revit families .
Is there some hint you can give, i rly watched many tutorials but i wont get this thing done right.
Thank you