Thanks for your post on our Community Forums and a very warm welcome to you!
Sorry to see you've been struggling with the device management on your TV Go account. Can you tell me if you've been able to access your account through a web browser to make the changes to the devices?
If so, can you try clearing the cache on the browser to see if this can resolve this issue for you?
If you've attempted this on the application, it may be worth uninstalling and then re-installing the application as well as then logging back in. I'd also advise checking that you have the latest version of the operating system you're using also.