Hi, I'm Nathan.Sorry to hear that you're having trouble with this but I'll do my best to help you.
You only ever need the link code once, for the first time setup. The purpose of that is to register the roku device to a roku account, which won't change after it is done initially.
If you have moved, what you need to do is to connect the roku to your new home wifi account.Turn the roku on and go into the roku settings menu under network/wireless, it should scan for available networks, pick yours, and enter your new wifi password.
Let me know if that helps.