Yeah, that happened. Story time.
One Friday evening I was sitting at home enjoying dinner and watching tv, almost like a normal person. Then suddenly I lost internet access for no apparent reason. Since I do have two separate incoming internet connections (one fibre and one cable ASDL) from two very different ISPs I was like “huh?”. Around the same time my monitoring system pointed out that the router was not reachable. Time to figure out what was wrong.
A visual inspection of the router gave zero clues as it looked like it was working. LEDs flashing as expected but the GUI was not reachable. Neither did the device respond to ping. A restart did nothing but now the status light started to flash white. Oh, I had this one before when the power supply was broken so I quickly dug up another spare one and plugged it in. Same response, not good.
At the same time I saw on Facebook that people not in my neighbourhood but an adjacent one complained about power loss. I still had power and had not experienced any problems. Checking the power company website I saw that there were outages both south and north of my area. These problems started at 19:17 and when I check the monitoring system it turns out that was the same time as my router became unresponsive. Odd but it had to be related. No other equipment in my setup reported any kind of problems around that time.
The next day, Saturday, I went by my local computer shop (Webhallen) to pick up a new router and went home to install it which thankfully worked straight out of the box. Adopted it into my Unifi network via the controller I had set up on a RaspberryPi earlier this year and I was back online again.
Post mortem: when I finally had my network back up I went to see what was really wrong with the old router. It turned out that a factory reset brought it back to life again. So if I had tried that first it would have saved me the cost of a new router but now I have a spare one if I ever need it.