There are several potential ways to inadvertently obtain simplex vs. duplex output:
I created an automated workflow recently to impose a repeated 4x11 pdf document 4up to fit a die cut press sheet: 10pt. C1S Cover 12 x 18. The pdf is two pages and will duplex. However, every time I send the test file, it prints the front and back on separarte sheets - exactly as setup, save for the duplexing.
NOTE 1 - We have printed this job for years with no issues prior to our transition automating our workflow using a manually setup queue on our Color1000 press.
NOTE 2 - This is not my first automated workflow like this, I have setup at least 20 others that are fully functional for single page and duplex files, in sizes ranging from 4x6 to 8.5x11. This particular situation is particularly fustrating since it seems such a simple operation.
Any advice would be appreciated.