Chime Pro will not connect to router

I tried to set up the ChimePro in the hall, about equidistant from the front door and the router in the room above. It will not connect to the BT Home Hub 6 router.I then moved the ChimePro upstairs and placed it 18 inches from my router. It connects to the app but not to the router because of poor WiFi signal!!!As the Doorbell3 will connect to the app and the router I do not see why the ChimePro fails to connect to the router whenthey are almost touching.Is it faulty? If so is there any way I can find out?Any suggestions would be welcome.