If restarting the wireless connection and/or your cable modem (or whatever you use) doesn’t help (and there is a reason it might), you need to work with your ISP. They can confirm your settings are correct. Also some troubleshooting steps like eliminating the wireless router (if it is not also the “cable modem”) may require coordination with them.
Yes, adding to what Darth said:
After you restart the modem, try plugging your computer directly to it if you still have cords, ALSO reboot your MAC after the modem is up again.
I go through this once a year with my ISP (Comcast) ... where power cycling the modem doesn’t do it and they have to send a reset message to the modem.
USUALLY when we do that, I also have to reboot my mac because it’s caching some of the connection information from the prior configuration.
In short, as Darth said ... power cycle the modem (I add - reboot your macs before declaring defeat after the power cycle) then call you ISP. Probably a piece of cake - they’ll send a reset signal to your modem’s and you will be happy again.