If your Mac is turned off when you connect the adapter, your keyboard and trackpad won’t become active until after you hear the tone. After the tone, you can press the power key or the Touch ID button to power up your Mac.
It's best to use the Apple AC power adapter that came with your computer.
- Identifying the right power adapter and power cord
- Using the USB-C port and adapters on your MacBook (Retina, 12-inch, Early 2015) and later
- Get help starting your computer if it still won't turn on after you connect it to your power adapter.