Having a recurring issue where my lines drawn in Layout will default to a lineweight of 1 with a white fill, regardless of the actual lineweight and fill settings that are on. Lines can be edited after creation, but the only way I have found to draw them correctly from the start when this happens in a file is to copy all my existing work into a new file.
What happens if you select the Line tool and then make the lineweight and fill settings before drawing? Note that you must have a drawing tool active to make any changes in the Shape Style panel that will affect subsequent drawing. Changes made in Shape Style while no tool is selected will have no impact. And while you can edit lines after they are drawn, those changes only affect the selected lines and have no impact on the settings still applied to the drawing tools.