Macbook Sound Greyed Out

Hi! Thank you in advance for trying to help. You're amazing.

My Macbook Air (13-inch, Mid 2011) running High Sierra suddenly has no sound anymore. I really didn't notice what might have triggered it.

Important information:

The volume icon on the task bar is greyed out.

Preferences > Sound > Output only display my Apple TV as an option

Pluging an earphone doesn't change anything

Tried reseting the NVRAM (screen blinked a lot, but nothing changed - How to reset NVRAM on your Mac - Apple Support)

Tried some terminal commands (https://discussions.apple.com/thread/4202694). Nothing happened.

There is no red light in my phone whole

Tried manually deleting Library->Preferences: Audio