why Content library 360 is not showing in my Articulate 360 desktop App

The Content Library 360 link only went to a page that listed Content Library but really was more informative than practical in the sense you didn't use that to access any Content Library assets. Thus the link was removed. 

The 360 app that still shows it needs to be updated and it will be removed. 

With that said, all of the Content Library assets are intact and still integrated with the authoring apps.