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.
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.