The Cisco 887 is a popular Router for a VoIP specific broadband connection, the lights can really help find out what's happening.
CD - Solid - Sync
PPP - Solid - Authentication
OK - Solid - Power
Data - Flashing
If OK light is off/flashing then issue with power to the router – Check power supply/where it’s plugged in.
If CD light is off/flashing then issue with sync to the router – raise a fault to your ISP then onsite checks.
If PPP light is off/flashing then issue with authentication to the router - raise a fault to ISP then onsite checks.
If Data light is off then raised a fault to ISP.