Open vectors can’t close

These lines are not connected:

they are intended only to do/only suited for no-offset contours so as to serve their purpose in this design.

You could export the vectors to a 3rd party tool and expand the strokes as discussed at:

Please note that I am removing the two posts with the commercial/copyrighted file — we can’t have such files distributed thus — use opensource/Creative Commons or your own designs if you wish to upload them for distribution.