You may have tried to change your wordpress username in phpadmin and found that you no longer have the Network Admin option on the Dashboard menu. If you did, you need to check with the procedure below and see if you followed it correctly, to change your multiuser admin username:
Edit the follwing:
Find the row corresponding to “ID” of 1. On the same row, edit the user_login field and change “admin” to a new user name.
Find site_admins field containing the string “admin“.
It may be like:
Note that the 5 just before admin is the character count of admin. So you need to change admin to your new user name, and substitute 5 by the new character count of your username.
There, that’s it! Now you’ve successfully changed your admin username and thus hardened your wordpress installation a bit further. If you need to secure it further, pick an alphanumeric long username, and a very long password containing alphanumerics and special characters.
To drive home the point, I will reiterate. If Network Admin menu is not visible under “My Sites” on WordPress, the main thing you need to check is whether your username and its character count are correctly set in the table wp_sitemeta, field site_admins.