My guinea pig wont use his ramp?

I got my new hutch today which is exciting and after 4 hours my guinea pig wont go up or down the ramp. he used to live in a tiny 1 level cage. And the cage hasnt got much grpis on the ramp because its mainly aimed for bunnys. But thats no good for a guinea pig, what can i use to make it more stable and him more confident.