Sorry, but this is a bad drawing.
There are many elements that don’t align properly and you have many Tee joints. Tee joints cannot connect in a fill path. A fillable path must be one continuous line that joins in the same place it started.
OK, Try this. Preview the print and when the open shapes error appears, click show me. This will highlight all the lines that are set to fill, but are open shapes. Click any other layer color. This will change those lines to a new line layer. You now have 2 layers, one set to fill and one set to line. Adjust your settings and burn away.
Ahh, I didn’t understand the issue the first time. I thought you were trying to fill the entire image. My solution above should work for you.
If you want an outline around the filled areas, duplicate the entire project and place the duplicate on a line layer and temporarily disable that layer. Perform the steps above, but instead of moving the selected items to a new layer, delete them. Then you can reenable the hidden layer and you will have lines around everything and still have your fill areas.