Unplug, plug in again, it will work fine. It happens to mine too.
This , I think the routers get confused( LOL ) ,so unplug and plug in again is best fix ,goes for all brands
I plug my router and cable modem into a separate switched powerstrip - which is plugged into a UPS. That way I can shut them off easily (reboot) without affecting the other equipment connected to the UPS. Switch off, count thirty seconds, then switch back on.