After the 30 day free trial has expired, there will be a $99.00 (US) per month charge for the integration to run.  If for some reason the billing information was not filled out during setup, or the billing information has expired, the sync will no longer run.  Please note this is also required to get the 30 day trial to be enabled.   If you are still experiencing issues, please contact support via the portal (http://support.hubspot.workflowmax.com) for assistance.