Hi, someone told me that Beijing Bus No.867 doesn't go Mutianyu anymore.

I've never heard about the stopping thing recently.
Generally speaking, this bus route operates from March 15th to November 15th every year.
During this period of time, there are 2 buses departing at 07:00 and 08:30 that can take you to the scenic area directly. And the schedules of the return trip are 14:00 and 16:00. Have a nice trip!