Brand: DBC

Model: HGU-V210-4C

Type: Dual-band ONT Router with VoIP

Wi-Fi: 2.4 GHz and 5 GHz

Ports: LAN ports, phone (VoIP) port, and fiber optic input

This is my wifi router model name and number and I am not able to connect the extender.

It was connected but showing internet not available 

Please help me out