What version of windows are you using?
Try connecting to Microsoft.com using their IP address as a test.http://188.8.131.52
Check your DNS information by running this command in a Command Prompt window.
Write down your current IP addresses including DNS and Gateway.
Are your DNS addresses static or DHCP?
If they are static, it could be the ISP changed the addresses and they no longer work.
Try inputting 184.108.40.206 as Preferred DNS, then check the internet.
Access the router via the configuration page.
Check the addresses the router is assigned and using for the connection.