You need to click the Save button at the bottom of the page after you remove the static IP address entry.
To your previous post, yes MAC address can be changed. Sometimes you can change it to anything you want. It seemed that your grand daughter’s iPad was taking the MAC address that belonged to April_TV. You can check the actual MAC address used under a WiFi connection when a “private Wi-Fi addresses” is used.
To deal with the situation where a random MAC address may be used for a device, you can put the most restrictive policies on the Anonymous profile. Thus if a user wants to have less restricted access to the Internet, they’ll want to to use the native MAC address on the device.