Hi malclev,
Thanks for your post and welcome to the forums. It's really great having you on board with us in the Community. 
I'm sorry to hear you are having an issue getting your device registered for use with TV Anywhere. I think we need to start all the way at the beginning as if TV Anywhere has never been used before.
Can you delete the app from both your devices. Once you've done this, restart the devices by turning the power off and back on. We're also going to restart the TiVo® by turning the power off and leaving off for 5 minutes. Turn it back on and allow to full set back up.
On a PC or Laptop, go to anywhere.virginmedia.com > My Profile > Device Settings and delete the devices from the 'My Registered Devices' section.
At this point we're only able to add one device change for you so choose either the iPad or the iPhone to have the app on for now.
Re-download the app on the device you are going to register. Once this has downloaded, sign in using your primary account details. Go to the channel listings and select Channel 4 > Watch Now > Watch On Device. This should then prompt you to register the device. Follow the prompts on the app and this will register the device for you and streaming should then commence 
Let me know what happens at this point.
As we can only add one device change per month, you'll need to wait until April 1st to add the 2nd device.
Thanks,
Kath_F
Forum Team
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