Need to follow a sequence - see this....
Switch on and set up your own router or first Mesh unit (in its settings) to have its WAN port set to be in.. Dynamic/Automatic IP or DHCP (& Nat) mode, it may be pre-set that way anyway. Then, disconnect all cables from your new router (and all Mesh units) and switch them off and unplug them.
Then, put the VM Hub into modem mode ( https://www.virginmedia.com/help/virgin-media-hub-modem-mode
) and wait for the base light to turn magenta/purple (on a Hub3 - but not on a Hub4!).
Once it’s in modem mode, the VM hub “MUST” then be powered off. Switch your router on and make sure it’s fully initialised (leave 5 min) and then put in the Cat6a ethernet cable from its WAN port to the VM hub (any port will do).
NOW… power up the VM hub and wait 5-10 minutes for The Hub to initialise and and you should get a connection. Use the recommended App to connect any other Mesh units to the first one. This order only needs to be done the first time you connect the router to the VM hub. You might also set the SSID and key/password on the new router/Mesh to match that on the HUB so when you swap over, all your wireless devices should just connect automatically.
I do not work for VM. My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired, 1 WiFi, 1 on PA) Hub5 in modem mode with Apple Airport Extreme Router +2 Airport Express's. On 250Mbps, Talk Anytime Phone, x2 Mobile SIM only iPhones.