my brother printer MFC J 4620DW stopped printing from my macbook pro

It ought to work, as long as you installed that printer as an AirPrint device. To learn how to do that please read Connect an AirPrint printer to a Wi-Fi network. Be sure to specifically select AirPrint.

If you are certain it is already installed that way, simply restart your router: power it down, let it rest a moment, and then power it back up again.

While you're at it, you might as well restart the printer in the same manner.