Sounds like your router reset its MAC clone.

Plug into the router and type 192.168.2.1 into your browser. If it doesn't work, but you know your computer's network card works, then your router is fucked. Once you get into your settings, you'll be able to clone the MAC address of your laptop and then your ISP will recognize your router as your laptop.

This is fucking annoying, especially because they don't ever warn you about this process, and I used my work computer to set up my internet.