I also checked the 'Sound' menu in System Preferences, but in the outputs tab everything is perfectly fine. What should I do? No volume is playing on my Mac.
If 'System preferences > Sound > Output' shows no output devices, try a reset of the nvram.
- 'volume stuck on mute, cant untick the mute box in sound settings (macbook air)' https://discussions.apple.com/thread/8593873
- 'Reset NVRAM or PRAM on your Mac' https://support.apple.com/en-us/HT204063
- 'iMacの音量表示が斜線になりiMacから音が出なくなった時に試したこと' https://www.chawanmushi.net/entry/2018_0602-imac-sound-setting/
If you have a connected audio device/audio interface that has it's own volume control then you cannot control the volume of that device from your keyboard.