It would r to give you the exact fix if we could see the SketchUp file. Here are a couple of common reasons faces don’t fill. The first is that the edges you’ve drawn don’t complete a loop. A loop with no gaps is required in order for a face to form.
The other common reason is that one of more point edge on the loop is not in the same plane with the rest. If you didn’t manage to keep all the arcs on plane, you won’t have a face.
You can identify where the problem part is by drawing with the line tool across the shape.