vpython in cocalc

vpython introduces specific html elements, which are designed to only work with the classical jupyter notebook. On CoCalc, we use our own implementation which leverages features of the platform, but utilities like vpython are not aware of this and CoCalc isn't compatible.

You either have to switch to "classical jupyter notebooks" (that's in the "file" menu of that worksheet, at the very bottom) or start the standalone jupyter notebook server: for that, goto project's settings ( wrench icon ) and at the bottom is a link to it.