Free Fax License from Digium

We are running FreePBX on and have set up a Fax for Asterisk module from Digium with the free licens. But after it have been working for some weeks we get the followin :

ERROR: No Fax license detected. Fax-related dialplan will NOT be generated! This module has detected that Fax for Asterisk is installed without a license. At least one license is required (it is available for free) and must be installed.

Why is this suddenly not registred anymore - and is it possible to re-registere the license.
The licens is still in the path

Can anyone help?