Trying to reset my moms laptop, flashing folder with question mark

Hi! I tried to “factory reset” my moms old 2019 MacBook Pro using these instructions above^, however, the MacOS reinstall seemed to stall. There were “16 seconds remaining” for hours, so I shut the laptop down. When we tried turning it back on, the screen flashed a file with a question mark on it. I’m unsure what to do now. Does anyone know what next steps to take to get the laptop to where it’s “reset” without my mother’s info on it? We don’t need the old files back or anything.