On a Chinese forum, a user had the -9000F issue as well. Translated, you may want to try formatting the hard drive before restoring if you don’t care about your data. I have this problem but I did not get to try it as the Apple Store has already sent my machine off for repair.Hi guys, i don't know if i messed up big time, or if I'm just not seeing what i did wrong. Anyways I was trying to install macOS Catalina (10.15) on my 2018 MacBook Air, but I didn't want to install it on my boot drive so I installed it on a external ssd, before I could I went into recovery and enabled External Boot: Allow booting from external media, after that i installed Catalina and everything went great, I did what I had to do and when i tried to turn off External boot i tried going into recovery once more (with the external ssd unplugged) and it started doing internet recovery. I let it do its thing and when it finished it gave me an error of -9000F and apple.com/support, i couldn't figure out the issue, i plugged back in the external ssd and tried going into recovery, and to my surprise it worked, i went into Startup Security Utility and it asked for my admin password on the external ssd not internal, i put it and it doesn't accept my password, no matter what I put it doesn't work, any ideas why?? its not a big issue as the computer works normal, but I would like to fix it. Any help is appreciated.