An open vector is a vector that does not join back with itself and the easiest example to visualize is a line. A closed vector is one that joins with itself to form a shape with good examples being a circle or rectangle. Sometimes you can have what looks to be a closed vector but is in fact an open vector. This can cause problems when setting up toolpaths, as some toolpaths treat open vectors differently from closed vectors.
The message "Ignoring Grouped Open Vectors" most commonly occurs when creating text using the Single Line function and the Vcarve Engraving toolpath. There are many ways to join and merge the lines to create closed vectors but sometimes the simplest way to correct this is by switching back to True Type or trying a different toolpath such as the Profile or Quick Engrave toolpaths.
For additional help with open vectors in your Vcarve/Aspire project, please reach out to Vectric at Support@Vectric.com as well as the list of resources below.
Vectric Widget - Tutorial - This video briefly covers joining vector lines at 7:40 in the video.