Thank you for contacting us Edouard, our team is happy to answer any questions you have about working our WordPress backup plugin Total Upkeep!
Once the Total Upkeep plugin files are removed from your website the Connect key associated with it is no longer actively used. One thing to keep in mind that the Connected Websites list in BoldGrid Central is simply a history of any website that ever used that and does not necessarily reflect whether or not the connection is currently active.
Please let us know if you have any other questions for us!