Well, everything is arranged (or almost!)
The licenceactivation@solidworks.com track is a dead end!
On the other hand, as I don't remember who suggested to me, I contacted the dealer at the time. Very very good reseller by the way: contrary to what I thought, even though they are no longer under a maintenance contract, they still take care of the problem. My company having changed its name and being bought in the meantime, they still managed to find us in their archives.
As a result, they were able to do the maneuver to delete the "token" on their server. And also to clean up the management that had been done by my predecessors. In short, real happiness .... And all I have to do is enjoy my new war bomb machine.
Thanks to all the guys anyway:)