I've been an NBN customer for a number of years and recently my VOIP line does not connect. The phone has a dial tone, but there is no Phone 1 light on the modem (Archer v1600v). When I dial a number instead of connecting to the phone I'm calling I get a long continuous tone.
Internet works fine.
It sounds like the phone port has not been enabled. Your modem has a unique number (MAC address. on label underneith modem) that has to be registered on the system. You will need to contact TPG to resolve this
You could try photographing the label, and e-mailing it with a description of your problem to TPG.