Why is no toolpath being calculated for the vectors I have selected?
There could be a few issues that would cause this and most should generate a Warning or Error message.
Some quick things to check include:
Tool too large to fit in the area. Try increasing the size of the area slightly or Edit the tool and very slightly reduce the bit diameter just for that toolpath. For example, if you are trying to cut a pocket 0.25" (6mm) wide with a 0.25" (6mm) end mill you can adjust the pocket width or 0.251" (6.02mm) or edit to tool's diameter to 0.249" (5.98mm).
Use node editing to check the vector(s) for small loops or overlapping segments. This is a very common problem when the vectors have been exported from another program.
If nothing is apparent, this type of problem is always good to post on the main forum and if the file does not contain any protected images or models, posting the file helps considerably. As a minimum, including some pictures and screen prints will help other forum members offer suggestions and ideas.