Combined paths skipping lines

I combined the path of two objects in Inkscape, and the common line between the two objects is visible in Laserweb, but when it cuts, it only cuts the outline and not the line joined between the two objects.

How do I fix this?

Just make sure that you don’t have multiple lines on top of each other in Inkscape.
Inkscape does not optimize the lines when you combine them and the path optimizer in LaserWeb drops two lines that are on top of each other.