Hi guys,
The total billing appears as $0 for the tasks or timeslots which were created before the billing category was assigned to the user. After that, billing amounts should start working correctly,, if this is not the case then we probably have a bug, but I guess this is what might be happening.
Billing amounts are set the moment the tasks / timeslots are being closed, because they could change with time and previous timeslots should not have their billing values updated. We could probably add an action to set all "0" billing values to the current billing settings for a user though, do you think this should be a necessary feature?