If subscription provisioning failed for several times in a row (10 by default), it gets to status Provisioning failed - canceled or Prepare and provisioning failed - canceled. In this point system will not retry provisioning anymore assuming that something is wrong. However, administrator is able to reset provisioning status to Provisioning failed in order to initiate several more attempts (again, it's 10 by default). However, it is recommended that problem that was blocking subscription provisioning is solved prior to resetting. Here is how you can reset subscription provisioning status:

1. Go to Admin Panel, Subscriptions page
2. In search field put subscription's id
3. Once search is complete, put mouse over Actions in ID column
4. Drop-down menu will be shown. Select "Reset provisioning status" option