For some reason, all available layers do not appear in the Layers Panel pull-down. What do I need to do to make them show up? They are present in Explore Layers window but not in the panel pull-down.

Sorry, no answer here, but I too have noticed this a number of times.

Probably an update is required.
Please review the FAQ section on how to update CMS IntelliCAD.

Also try to delete the "CMS IntelliCAD" folder that is located at your Windows documents folder.
Then run CMS IntelliCAD again, and or software will restore the folder and default files.

Apparently I have the latest release, no update available.

Steve