Cannot Change User Name OS 10.12.6

[trixman]

Sierra 10.12.6.
I followed these instructions:
1. Log out of the account that you're renaming: Choose Apple menu  > Log Out.
2. Log in to the other administrator account. Do not log in to the account that you're renaming.
3. From the menu bar in the Finder, choose Go > Go to Folder, then type /Users and press Return. The Users folder opens.
4. In the Users folder, select the folder of the account that you're renaming, then press Return and enter the new name. Don't use any spaces in the new name. When prompted, enter the name and password of the administrator account that you just used to log in.
Step 4 failed. I selected the folder with the name I wanted to change but nothing happened when I pressed enter.
HELP!

 

[Bigwaff]

Turn off File Sharing.

 

[trixman]

Thanks, I tried that, all turned off, but it was still a no go.
When strong passwords and logins became important years ago on my Windows & Mac machines I used to use complex IDs and Passwords for security reasons. I have found from experience that complex ones were mostly unnecessary and with the improvements in security I have been replacing them with simplified ones. My Mac pro is one of the holdouts.