I have an area whose outline is formed by two straight lines and two arcs:
I want to fill this area, however, when I use the hatch tool I get a message saying the outline is not closed. I believe the lines and arcs are connected at the extremes, but I add my .dxf file here so you can help me more easily.
The issue here is with the ellipses. The hatch tool doesn't have the math to calculate the border of the elliptical arcs.
One trick is to save the file in DXF R12 format. The DXF R12 format doesn't support ellipses and replace them with an approximation of short line segments.
After close and reopen the R12 file the hatch works and the file can also be saved in DXF fomat 2007 again.