Legend, thank you. Had this exact scenario with the same thermostat and got it paired thanks to your video. The instructions with the new Hive Hub are terrible.
Pairing the devices is easy. But you didn’t show the difficult bit of how to add the new hub to your system so you can control it with the app and website. Suggest you change the title of the video
For anyone wondering, you have to phone Hive and get them to remove the old hub from your account. Only the can you add the new hub. You do this by plugging it in and waiting about an hour.