[BH] Can't hold tattoo class despite having three tables

My Sim has a tattoo skill of six. I opened a small business out of my house and have everything set up. I bought a whiteboard and a digital sketchpad. When I go to start a class, it’s not allowing me to. It tells me that I need three tattoo tables which I thought that was the problem so I bought a third one, but i’m still unable to hold a class. Is there something else that I’m neglecting to do?

Edit By Crinrict: Adjusted Title to better reflect the issue