E3M2 Shotgunners Cubicle Platform problem

So I've made it to E3M2. Completed the map. 100% kills, 100% secrets but only 60% items! Then I realize the platform with all shotgunners in the cubicles at the entrance to the cave in the top right won't lower and allow me to grab the items in those cubicles. I watch BigMacDavis's video and the triangular column to the right of this cubicle platform seems to raise up and gives you a red plot of ground to step on and lower the cubicles. But on my map (Ultimate Doom from GoG) this triangular column won't raise! How do I activate this? What am I missing? For Mac it just happens, but no matter where in that area of the map I "use" or step...nada.