Can't reset to factory settings as keyboard has stopped working

Following the instructions on 'What to do before you sell, give away, trade in or recycle your Mac'. I have completed steps 1 to 4, didn't unpair bluetooth. Mouse is working. Turned off computer overnight now keyboard not working.

I can't erase the mac or reinstall the factory settings as keyboard has stopped working

Scene asks me to setup bluetooth keyboard but the keyboard is attached to computer.

Using macOS Catalina on 27" 2013 imac