Although you have your answer, I into similar problem.

I was able to draw a triangle onto the screen; but the pushed vertices were being ignored.

Solution for mine was to bind the vao buffer before invoking draw and use

Although you have your answer, I ran into a similar problem.

I was able to draw a triangle onto the screen; but the pushed vertices were being ignored.

Solution for my situation was to bind the VAO buffer before invoking draw and use.