Ring 3 new set up failing to connect to wi-fi

Hi I am trying to set up my new Ring 3 video doorbell. I have the app and, with the battery fully charged and inserted, I followed the instructions to connect to wi-fi and each time I get 2 flashing white lights on the right and message saying failed to connect. The unit is sitting 2 feet from my router. I carried out a router reset. I carried out a Ring unit 15 second reset. I have a good router signal strength, disconnected all other devices in the house. I have re-configured my router to use a 2.4 ghz connection for the Ring. I have turned off “mobile data” or “cellular data” on my iphone. When I try to connect to my router using the settings app on my phone, the Ring sees the router and connects fine. I have re tried numerous times, with the same result, two flashing white lights. Is there anything else I can check, please check what I have done already before making suggestions, it’s not helpful to request I cary out the stages I have already done. Cheers