Claim account

Remember: for security reasons, it is possible to link a Monopoly GO! link to only one Sticker GO! account (regardless of the language used).

So if you send the request and the link is already associated with another account you own, the link will be disconnected from that account, and you will no longer be able to use it; to continue using it, you will need to enter a new link different from the previous one.
You can also free up the link on your own by deleting the account you no longer want to use.