Steps to take. First bypass the router and connect a PC direct to the modem. This is to ensure you have a good internet connection and the issue is not with the ISP. Be sure to use a good Ethernet cable as they can cause a lot of issues including the one you have. Next with the PC connected to the router, sign on to the admin page and review your settings. You may have reset it back to factory by pressing and holding the reset button. So you may need to reenter your settings.

You can see the power light is not even lit.

Sounds like it may be bricked. If new, start a return process. If not, there are procedures elsewhere to try and unbrick a router. I have had to unbrick one and there is mixed results if it works. Hope it works for you.

If you have a different power adapter of the same voltage and apps, try that.