Issue with linking Virgin media account to Virgin O2 ID

(New customer on Virgin) 

I've recently had the hub5 installed and wanted to manage my account online but each time I try to link my Virgin Media account to my Virgin O2 ID, I keep getting the message: "Email address doesn't match" as shown in the image attached.

I've only used one email address for everything Virgin related so I'm not sure why this issue keeps coming up.

I've tried doing it through the app on my phone and I have the same problem. The problem persists on my laptop and 2 other devices.

Could I get some help on this please?