In AutoCAD 20 19, the problem that the solid is displayed as a dotted line when it is stretched may be caused by the setting of visual style. You can set the display back to the blue line when you stretch a solid by the following steps:

Switch to the Visual Styles tab: In the top menu bar of AutoCAD interface, click the Visual Styles tab.

Select the appropriate visual style: In the Visual Style tab, view the currently selected visual style. If a style is currently selected, such as 2D wireframe or 3D wireframe without shadow and filling, the solid may appear as a dotted line. You can try to choose solid color, 2D fill, 3D stereo and other styles. These styles display solid lines as solid blue lines.

Adjust visual style settings: If you need to further adjust visual style settings, you can click the "Visual Style Manager" icon in the visual style tab, and then edit and customize various visual styles in the pop-up window. You can modify the display effect of styles, such as line color, line type, shadow, fill, etc.

Through the above steps, you should be able to set the display effect when the entity is stretched back to the blue line. If you encounter any problems during the operation, you can always come back and ask!