Can't get Terrain (Global map data?) to work

I went through the simple Melbourne tutorial. In mine I noticed the background after the city is blank. If it’s not the 3D city it’s just stars. It’s like the Globe doesn’t show up at all. I can get Cesium OSM Buildings to work, as well as Melbourne Photogrammetry. Can show and hide with the check boxes. But nothing happens when I click Bing Maps Aerial with Labels. I also tried Blue Marble Next Generation July, 2004.
I signed in to Bing and got a map key, though I’m not sure where to put it, or if that’s even my problem.
New here and know almost nothing about coding.
The story:


Hmm. Just now it worked for a bit. Had 2 windows of a D.C. one I had open, and it was working on one and not the other. I hit reload on the one that was working and the background went away again. Um, help?