NVRAM: Error clearing firmware variables: (iokit/common) not permitted I cannot reset my NVRAM at startup (holding down ⌘ Command⌥ OptionPR does nothing), but I want to reset the NVRAM so I am trying to reset it with Terminal.

$ sudo nvram -c
nvram: Error clearing firmware variables: (iokit/common) not permitted


How do I reset the NVRAM?
Despite the error message, the NVRAM has been cleared. Found this on another forum that proves it out:
$ sudo nvram TestVar=HelloWorld
$ sudo nvram -p | grep 'TestVar'
TestVar HelloWorld
$ sudo nvram -c
nvram: Error clearing firmware variables: (iokit/common) not permitted
$ sudo nvram -p | grep 'TestVar'
$