Yah, my first coop was an A-Frame, too. (Don't call it a tractor, because I built it GOOD and that sucker is permanently THERE in that spot!) During the day trips outside as growing chicks, they played on the ramp, but never went up it into the upstairs living quarters.
So I panicked and bought a coop kit on
eBay, with an attached, covered run. When I put the young chickens out full time, I put them in that coop. Day-times, they still played under the A-Frame and a little distance up its ramp. Several weeks later, one brave pullet went all the way up that ramp.... and pretty soon more followed. But they were already sleeping in the other coop....
When I bought two laying pullets a bit older than my chickens, I segregated them in the A-Frame, so it became THEIR home. They laid in the nest boxes.... then the other girls, as they started to lay, they laid their eggs in the A-Frame with the Lakenvelder sisters. They use the ramp daily. The Lakenvelders go upstairs every night.
Because they were a few months older, they were smarter. And had I not short-circuited the process with my original flock, they, too, would have learned to go upstairs at night.
All this to say: yours will eventually learn how to use the ramp. Honest!