Thanks for your post and welcome to the forums. It's great having you on board with us in the Community.
I'm sorry to hear that you are getting this error message. I think the best thing to do will be to reset things for you and go from there but in order to do that I will need to pass data protection with you.
I have sent you a private message regarding this and will investigate further once I receive your reply. Just click on the little plum envelope at the top right hand side of the page to access your inbox.
Thanks for coming back to me on this and apologies to hear that things still aren't working.
Are you able to navigate to see which devices you have registered? You may need to manually remove the device yourself. To do this sign in to TV Go. > Once signed in go to Settings > Device Management > Manage My Sky Devices. This should help to remove the registration.
Another thing to try is changing your log in password. To do this sign in to My VM. > Once signed in go to My Profile > Change password. Once this is done, try accessing Sky Sports again.