Hi @tomsaubi,
I try to answer your question without seeing your file.
Try to hold down Alt when selecting the sketch line.
That way you can select single lines.
Keep in mind when you like to have more than one line, you can select without holding down the Alt key and select the other lines that you like to assign to this selection.
Don't forget to press OK for the selection before calculating the toolpath.
Hopefully, this helps you otherwise upload your model.
Within Fusion 360, choose File > Export and save it on your desktop.
After that upload it to this topic so that one of us can take a look at it.
If my post answers your question Please use Accept as Solution & Kudos This helps everyone find answers more quickly!
Met vriendelijke groet | Kind regards | Mit freundlichem Gruß
Marco Takx
CAM Programmer & CAM Consultant

