I have chicks who one day they would all go into the coop at night, then the next day they would all be perched in the run. It may take a bit longer for them to learn but every night keep putting them back on the roost bars.
If the roost bars are too high up, silkies can’t fly ( or be able to use their wings to propel themselves up) to be able to jump up there. And sometimes it takes a while for them to understand when’re they should sleep.