The Studio Toolkit for Boxes Fold window gives an error that the Design cannot be folded because it doesn't contain panels or one of the panels cannot be selected as Base panel.
When using the Fold window to assign Cuts and Creases and try to convert these paths to an
ARD file using the Fold button,
If those do not work and the error still appears, check your paths (especially at cut path corners) to ensure the paths and not the strokes actually do match up point to point. Illustrator's Preview and Overprint Preview is unreliable since it displays the stroke weight, so it is advised to check the corners in Outline mode. Also note that our Check for gaps has a specific tolerance to be set in the flyout menu of the Fold window, so there may be corners that will still cause problems if not addressed.
Studio Toolkit for Boxes