You receive this error when managing functions from the cPanel for any of your account. This is because your cPanel account has been marked as Demo account. With the Demo account you cannot make any changes to your cPanel account. As the name suggests it is just to view the features available with cPanel.
Enabling/disabling the demo mode can be managed as root user via WHM. Login to your WHM as root & access option Account Functions » Manage Demo Mode. Select the account for which you wish to enable/disable the demo mode. Click on modify. From here, you can enable/disable the demo mode for any cPanel account.
You can use our cPanel demo account. They details are as below.