I thought it needed an exception but I'd tried to put the scanner app into the list of firewall exceptions. You correctly pointed me instead to scanning exceptions. It seemed strange but I added 10.0.038 (the IP of the printer) to the list and a quick test worked. For what it is worth, the error I was getting was unable to communicate with the scanner. That's why I thought it was a firewall issue.
Thanks for the quick response.