Cannot connect to internet on MacBook

If your ISP is down there is nothing you can do until service is restored.

If in doubt call them—they can look at your modem to verify service is coming in.

If your Mac doesn't connect to the Internet over Wi-Fi - Apple ...

have you rebooted the router?

you can have 100% signal to the wi-fi and an IP Address and LAN access but if your router gateway is down the internet is not going to be reached.