I added a user to the sudoers file using ['sudo gpasswd -a orca wheel']. This command was successful as per ""Adding user orca to group wheel"" but the user can not execute root commands still. I have logged out and logged back in.
%wheel ALL=(ALL) ALL was un-commented by default in the sudoers file.
I am using CentOS7.
Any help is greatly appreciated. I found the following article the best: https://www.digitalocean.com/community/tutorials/how-to-edit-the-sudoers-file-on-ubuntu-and-centos