Can you help me set up parental controls?

We set up our new Netgear Nighthawk router several months ago, set up an OpenDNS account to install the Netgear genie mobile app and enabled parental controls.  Some time later we began to experience frequent internet outages, and our service provider recommended a different brand of router.  We bought one of a different brand, installed it, and deleted the old router info from our devices.  A few weeks later, internet issues began anew.  We decided then to pursue a different service provider.  We have returned the new router, reinstalled the old router (Netgear Nighthawk), and now I need to re-establish parental controls.  HOWEVER (here is the actual question.....) I am getting an error saying that this device is registered with another OpenDNS account.  I've tried setting up a new one, and I no longer have my old user name and password that I used before.  HELP!  I would like to be able to erase all old account info associated with my devices and start anew.  I really need the parental controls enabled for my Netgear NightHawk Router, Model R7000