Check the front of the router and see if the global icon is lighted?
If there is no light at the icon, check if there is any cable plug into the WAN port at the back of the router or any cable loose at the port.
Check if the cable from router WAN port go back to the ISP modem router.
Also check if there is internet icon green and lighted. If there is no light or red light, please check with your ISP