need help to desactivate a/ activate a license

Dear SDL TEAM, 
I hope you are well.
I have an activated licence SDL PRO which has been installed in one of our PC. 
We have bought a new PC and need to desactivate the licence to reinstall it on our new pc. 
I have tried to desactivate it via the software on my pc but it says that : 
"La désactivation a échoué.
Revocation is not allowed for an expired licence."
 
Can you help me to do so Please? 
thank you
best regards
Malika akcha