When you install your NETGEAR DSL modem router, the NETGEAR installation assistant might display a No DSL Cable is Plugged into the Router ADSL Port error message, and the 
(DSL) LED might blink continuously or remain unlit. This indicates that your modem router can’t detect DSL service from your Internet service provider (ISP).
If you are experiencing a No DSL Cable is Plugged into the Router ADSL Port error, try the following:
Check your cable connections
Make sure that your incoming DSL service phone cable is connected to the gray DSL port on your modem router. If you connect the phone cable to any other port, your modem router cannot detect your DSL service.
Make sure DSL filters are installed
If your modem router includes a DSL filter, it must be installed in between the DSL wall outlet and DSL port on the modem router. If you also have a landline phone, connect it to the Phone port on the DSL filter. If you have multiple landline phones in your house, or you have other devices that use a phone connection (like a fax machine), you might need to purchase and install DSL filters for those devices as well.
Wait for new DSL service to activate
If you recently signed up for new DSL service, your ISP might not have activated your service yet. Check the information that you received from your ISP to see if it has a waiting period for new DSL service activation.
Contact your ISP
If your modem router still can’t connect, contact your ISP for assistance. Your ISP can verify your DSL service status and let you know if any service outages might be affecting your area.
For a visual guide to troubleshooting this error, see the following video: