A teen who cannot settle at bedtime is almost always dealing with one or more of: a mind still running on the day emotional or cognitive content, a body that is biologically not yet in its sleep window, or an environment, devices, light, noise, that is actively competing with sleep readiness. Sometimes all three at once. The inability to settle is a systems problem, not a willpower problem.
I am not going to tell you to just fall asleep. Let's figure out what is keeping the system running.