Presumably you also have broadband as well as DV , is your broadband working ?
Where is your phone instrument connected , at the rear of the BT SH2 router ( the green phone port ) or via a DV adapter ? …..if outgoing calls work , have you called your mobile or other landline and checked that the expected phone number is displayed on your mobile or other landline ( confirming the number you are calling from is the one you are expecting )
If the phone number is correct , call your own landline number from your mobile , ( with the phone plugged into the router directly not using the DV adapter ) , even if the landline is not ‘ringing’ what happens if you lift the receiver, or press answer if it’s a cordless phone , do you get dialtone or does the call connect .
