An can't add the traditional boot layer.

1. The guide wire is disconnected.

solution: enlarge the guide wire to see where there is a small gap and fill it.

2. The center point of the component does not fall on the guide line.

solution: use any deformation tool to select the component, and use the direction keys to move the component so that the center point falls at the beginning and end of the guide line (both the first and second keyframes should be viewed).