no admin account OSX 10.13.5 I have a macbook pro 2011 with high sierra  10.13.5

Today i tried renaming my admin account in the system preference / users. I couldn't rename the account, and i have lost the admin rights. Now i can access the account because i know the password.

I have the same problem described here : https://discussions.apple.com/thread/8238869. I tried the solution described in that page. The problem is after rebooting, the setup screen to add a new account doesn't appear. Instead the mac reboots normally.

MacBook Pro, macOS High Sierra (10.13.5), MacBook Pro (13-inch, Early 2011)
Okay, today i redid this procedure in single user mode and it worked!