Reset PRAM/NVRAM
The PRAM (Parameter RAM) and NVRAM (Non-Volatile RAM) hold information about various USB components.
It’s a slightly different process to resetting the SMC, but no less difficult.
- Shutdown your Mac.
- Restart it, holding down Command+Option (ALT)+P+R as you do.
- Hold down the keys until you hear a sound and see the screen flash.
- Listen for the chime sound and let the Mac boot up as usual.
