Faces not saved.

[sliptonic]

Create a closed sketch.
Select the sketch, right click and select 'convert sketch to face'
Do it again so you have two faces.
Select one face, right click and say 'extrude face' Enter a value and click o.k.
You should have a sketch, face, and solid in the tree.
Save the file. Close Heekscad. Reopen the file.
You will see the sketch and the solid but no face.