I’m not able to unlock a Schedule with a charger

Just attaching your charger is not enough. With the charger attached, you must go into the locked schedule’s detail page and press the little lock on the top right hand corner to unlock the schedule.

Occasionally, the schedule cannot be unlocked even if the charger is connected. Try reconnecting the charger with the locked schedule’s detail screen opened and wait for a while, then try to unlock it again.
You cannot use the charger to unlock a schedule which is locked for a set time. In this case, you will have to wait until the timer runs out.