I'm a bit confused as in your first post you said you see an error message - "An error has occurred please try again later" but now you saying you are seeing something different when signing into Sky Go.
For the latter issue it sounds like you need to accept the address before you can progress further and use Sky Go as Sky likes us to provide then with a non sky email should it be needed for account recovery reasons, it doesn't matter if you use it regularly or not so long as you can access it should you need to.