Did you see a read only file system error when typing in “rm /var/db/.AppleSetupDone” in single user mode?
Sometimes if you start over, it will work but you may be getting the error because you are using a Mac with a T2 chip and it won’t work on Macs with a T2 chip because the T2 chip does not allow write access to the drive.
This error can be caused because FileVault is enabled or that there was some random error. Try running the same commands in Terminal in the macOS recovery partition and see if that works. This error may also occur on a Mac with a T2 chip. If FileVault is enabled, you will have to erase the hard drive/SSD and reinstall macOS if you forgot your password.