1. Factory reset and set it up again.
2. Install DLink's latest firmware, factory reset and set it up again.
Router die quite often so when I make a call on such I carry a spare router.
I have a D-Link Dir 825 AC1200 H/W rev. G1 dual band wireless router and a static IP fiber connection. It was working fine for over an year and now suddenly it stopped connecting to the internet. Directly connecting the computer to the modem via Ethernet works fine. I tried resetting and upgrading router firmware to latest available one but it does not work.
While experimenting, I found that whenever I change the mac address entry in the router, it connects for few seconds, then connection lost.
I contacted my ISP about this but they said I have to change my router. Any help would be appreciated.