crosshair didn't show

[ZhouXiaolong0]

I did these step:

1. clone the repo.
2. Open the index.html file in the docs folder
3. And I found out that the axial and coronal and sagittal view Synchronize well, but there is no green crosshair show up like you example.
   like this.
   

How do I solve this? can anybody help me?