my macbook pro won't start
I've used the option/command p+r format but all I get is a screen with closed lock and an empty spacebar underneath
Do you have Firmware password set? If so, turn it off.
About the screen you see when your Mac starts up
https://support.apple.com/en-us/HT204156
“To turn off your firmware password, repeat the steps above, but click Turn Off Firmware Password in step 3”
Section: How to set Firmware password
https://support.apple.com/en-us/HT204455
How to set a firmware password
1. Make sure that your Mac is using OS X Mountain Lion or later, then follow these steps:
Start up from macOS Recovery
by holding down Command (⌘)-R immediately after turning on your Mac.
Release the keys when you see the Apple logo.
2. When the utilities window appears, choose Utilities > Firmware Password Utility from the menu bar.
This utility is available only on Mac models that support use of a firmware password.
3. Click Turn On Firmware Password.
“To turn off your firmware password, repeat the steps above,
but click Turn Off Firmware Password in step 3”