When attempting to invoice a Workshop job, and the message "Not all time allowed allocated to technicians" appears, it is usually due to the following:
The "Time (allowed to tech) if different" box that appears when clicking on a request line needs to match the value that is specified in the "allocated" column corresponding to the request in the technician log section of the history tab.
If the request does not have any technician logs that have been allocated to it, then the box needs to be left blank.
Below is a video detailing this further: