Problems connecting R7000 to Virgin Medium Hub set up in modem mode

Background: had been successfully running home network on Virgin Media Hub 3.0 set in modem mode connected to Negear Nighthawk R7000 AC1900 router via ethernet cable to extend wifi range around old house with thick walls. All ran ok for 18 months until i tried, unsuccessfully, to upgrade R7000 firmware. Tried several options but all failed, then lost netgear router so did a factory reset. Nighthawk mobile app was unable to connect despite trying manual set up from start. Network indicates "connected without network".  Ethernet cable connected and all lights ok between Virgin hub and Negear router but cannot connect to internet. Checked Virgin hub was in modem mode again and retried but no success. Tried all windows diagnostic tests with resets but no success.

Had to reset the Virgin hub to router mode and use this (completely bypassing the netgear router) as the only way i can currently connect to internet (with limited range). I have read Netgear manual and tried several ways to fix, but ran out of ideas. Thought about trying to upgrade Netgear R7000 firmware via the USB port at back to see if that would help router connect again but not done that yet. Looking for any ideas. Not a technical expert but should be able to provide additional info if requested / needed to help solve problem. Thanks in advance for any help and tips.