After I launch my project in the constructor with the Baby 3D Plugin, I get a black screen, and when I start Debug layout, the download writes and the screen is still black.

Make sure all layers are invisible and check again please.

The plugin has its own canvas which is behind the C2 one, therefore the 3D content may be completely covered up.

I'll warn you right away that there may be Russian, but they don't seem to affect anything. https://drive.google.com/file/d/1hVzgNgVdIfmHjtGiFTRTCzlITwkwmMBx/view?usp=shari...

I totally dropped that the ball in looking at your project. 

Checking it out now I realize I cannot open it due to many third party plugins being used. Have you tried removing those for testing, saving it seperately as such and see if it works? 

Also I've asked before and I do take it that the included examples do indeed work for you.