Training Silkies???

I have an Egg Cart'n tractor that I have a Silkie pair and a Salmon Favorelle hen in. They have been in it for 3 months now, and STILL cannot/will not go up the ramp each evening to the "coop" portion. I have to physically catch them, and put them "upstairs" each evening. When I had my layers in there, they ALWAYS "self-loaded" each night...

Their food and water is "upstairs", which I thought would entice them to come back up. Nope. Doesn't matter. I don't want to leave them in the bottom portion because it gets too cold (though I do have panels to fully enclose the bottom as well as the top) and they are accessible to predators down there.

Do other Silkie owners have the same issue with them not being "self-loading" into the coop at night? Is there any way to train them?