I am a long time Qimage user and never had any real issues that weren't operator error.
I have just acquired an Epson SureColor P5360 (the Australian model of the 5300/5370).

My issue is that when using the manual feeder and I choose a gloss or luster paper, the printer loads it happily and awaits instructions from Qimage to print.  If I hit print, the file is sent, the Epson ink window pops up as per normal but the image will not print.

If I change the paper type to Matt or Velvet Fine Art, it all works perfectly well even if it is using the same glossy paper that was loaded for the unsuccessful gloss/luster print.

Using Epson Print Layout with the manual feed and glossy/luster settings works perfectly well, as it does when printing from both Capture One and Lightroom.

Is there something that I am missing here?

This is precisely the issue I was having. Thank you for your post. Just tried printing a matte sheer, and it printed fine went back to luster, and, surprisingly it printed also. Go figure.