Thanks a lot. It now works after using IE11 to manage the router

. I was using Chrome, maybe Firefox, which gave exactly same, visually, user interface and slider button.
Kind of disappointed that D-Link has significantly changed the UI to more graphic ones, although it is indeed easier for first timers, it has lost some features and controls that old D-link (DIR-625) routers have, and adds limitation on which browser to use

Anyway, thanks a lot for your help.
Model: DIR-880L
HardWare: A2
Firmware: 1.07WW
Region: Minnesota, USA
Purchased at: Best Buy in Dec 2016