B777F no apu

Apu switch is not starting the Apu. Normally you can hear the Apu starting. And of course, if it doesn’t start, the Apu light will not illuminate, and you can’t start the engines. I always use the ground power until I finish my flight plan, then I start the Apu. Any ideas

Aviate, Navigate, Communicate is the help area for aircraft. I moved your post.