Help - Someone else has already registered this device?

Hi, my TV was working perfectly fine with SmartThings and my Google hubs. There was an announcement on my Google Hub that SmartThings were updating so I needed to relink my account - so I did. After doing this, my TV couldn’t be turned on with my Google hubs, or from SmartThings (though when I turned it on, I could then use it).

I figured that the best thing to do would be to remove the TV from SmartThings and try again - bad idea. Now I keep getting a message on my Android phone (also tried it with an iPhone) saying ‘Someone else has already registered this device’.

Can anyone help as this is really doing my nut in!