If you have bought PitStop Pro subscription, you have received a subscription ID. This ID has to be activated in order to start your contract term.
To activate your subscription ID
The Enfocus ID is a new account that replaces all former Enfocus accounts
(the webshop, product activation and support portal account). From now on,
there's only one account for all communication with Enfocus. Note that there
is no way to convert older accounts into an Enfocus ID; even if you have
already an Enfocus activation account, you are asked to register once again.
Registering is very easy; just click the Get an Enfocus
ID link and follow the on-screen instructions. 

Note that you remain signed in with your Enfocus ID: you won't have to enter your credentials next time you launch PitStop Pro. However, if you haven't used the software for a longer period (more than one month), you may be asked to sign in again, so PitStop Pro can check if your license is still valid.