Hello I have a valid license till May 2015.
If I download the new version of PVM the key is not valid.
Have you downloaded the enterprise edition? There is now a free version in the same download page and sometimes people download it by mistake.
In the positive, are you entering the key in Help - Register version?
Customers that use Devolutions Server are provided free remote sessions for performing upgrades. Please send a request to the Devolutions Service Desk to get the process started.