Vertex Paint Not Working

So I am trying to use vertex paint to paint with two textures. I have watched every video on youtube and followed them to a tee, I have ensured that I am holding shift, and I know my imported box has more than enough vertices. It still wont work. What am I doing wrong? Did I import the asset incorrectly? Is left click shift not the right command to paint when the object is selected?


Thank you.

I also need help on this subject. Could anyone please help us out?