Hello all. I have had this same problem forever with Mac OS and all of my printers. The problem is the default setting on the Macs (at least mine) is set to double sided and this setting overrides Dorico’s setting. I did some digging about how to change it and came across this video showing how to change it on Macs. I would have never know without this video. But NOW IT WORKS! I do not have to do the work around of exporting to PDF first and then printing from Preview. Below is the link on Youtube.
