At a guess... Your Nokia Account log in is no longer valid on that phone because of the transition. Have you tried logging into your Nokia Account via PC browser? Have you tried the Ovi Store on PC?
You could try establishing a Microsoft Account (or use an existing one) and try to sync that on the phone...
My Nokia Account log in is still good, but I've long had it linked to a Microsoft Account. I also see Microsoft has taken ownership of Ovi...