Hello RodolfoDantas
From the message you are seeing, it looks like the tag is already linked to another Apple Account.
Apple Find My accessories can only be linked to one Apple Account at a time. Before the tag can be connected to your account, it must first be removed from the previous owner’s Apple Account.
Unfortunately, this is not something that can be resolved from the GPS-Trace side, as the Apple Account connection is managed by Apple Find My.
We recommend contacting the seller or the manufacturer of your Locateo TX04. If the device was sold to you as new, please explain that it appears to be already linked to another Apple Account and ask them to help remove the previous connection or replace the device.
We hope you can resolve the issue with the seller quickly.