Ramps Not enough traction?

I finally made my g-pigs a second level but I'm not sure if my ramp will work. Right now it's made of bent grids with a piece of coroplast over it and I've clipped a piece of fleece over the coroplast. I've managed to get Oreo to go up the ramp twice and I put Sundae on the second level to make him go down it but I feel like they don't have enough traction to get a grip onto while running up and down. It's only been up for a day but they haven't used it on their own. Is it because there's not enough traction, maybe? What is something better that I can use? I saw people have used bath mats and I found a post from years ago where somebody had used those cabinet liners. I just want them to use the dang thing lol.