Guinea pigs wont use second part of cage...HELP!?

OK so I have a C&C cage for my guinea pigs, and I thought to add more room to it I would build a second level. Well I did that and they WONT USE THE LADDER. I made the ladder first out of these wooden sticks connected together but that was to steep and then I used two bent grids that I covered with fleece, but they still didn't use it and then I used coroplast with thick lines across so they could use them to climb, AND STILL THEY DONT CLIMB IT! I dont know what to do now. I mean I build it and it took me a long time. If tried using treats and stuff but they'll go half way and give up. I've put there food on top and nothing. I dont know what to do. I've even put them up top and left them there for a couple hours only to find them still up there. Maybe its my ladder i dont know. If so, how can I make a ladder not steep that my guinea pigs will be comfortable climbing. I'm guessing its to steep for them at the moment. Serious answers please and thank you :D