Changing a 2D Drawing into a 3D Object

I have been an avid CorelDRAW user for many years and just bought a 3D printer.  I am now trying to turn a flat logo I created in CorelDRAW into a 3D image, so I just purchased CorelCAD 2019 to help with this, but am running into a problem for some reason.

I go into CorelCAD and import the image and use the CorelDRAW/Corel Designer Import command in the File menu.  The graphic seems to import without any problem.  I then adjust the view to an SW Isolmetric so I can see the graphic in 3D.   Here is a picture of the graphic in CorelCAD:

logo

The next thing I do is to go in and try to extend the lines of the solids areas in the logo.  I will click on the area and it is highlighted.  I then go into the Solids menu and select Draw > Extrude, and then I can either use the mouse to select how much I want it to extrude or I can type in a number. My problem is, not all the solid objects will extrude.  In the graphic, the only ones that seem to work are the ones that I have colored green.

I have done a little experimenting and have gone back into CorelDRAW and redrawn the curves on one of the objects that won't extrude into a ton of little straight lines.  I then imported the graphic into CorelCAD (which took much longer) and it seems to extrude then.  I have tried selecting the the objects in CorelCAD and selecting Explode, then I can extrude some of the lines of the object, but not others.

Is there something I, a newbee to CorelCAD am missing here?