Can’t access certain sites after an outage

I live in the Lake Forest, CA area and I have had the exactly same issue as mentioned in this post since last night (11/3) around 8pm. 

Our router and modem are two separate devices so it’s not an all-in-one modem. Wifi isn’t working at all since the router returned no internet connection errors. When I tested with a wired connection from my device to the modem, I can access few websites only (Google and Facebook). Some sites like Amazon.com, Costco.com , Cox and more including the sites I rely on for my work are inaccessible on all devices. 

I am not using a VPN either. I have also tried factory reset both the modem and the router multiple times already but still no luck. 

note: there was an outage in our area around 5pm on 11/2, a day before this incident started and we were notified that got fixed at 6:30pm within 2 hrs (11/2)