I had attached a print screen of the setting.

Basically, my router does not save my Max Idle time to 0, and keeps it at 15, even tried to change it to 99, same result. It keeps it at 15.

I had pressed the save button(doesn't show up in my print screen, it's lower) numerous times, restarted router several times, upgraded my firmware version, and still, the same.

What Must I Do!