It really bites to waste a large sheet of specialized material on a project that just should work according to all forecasts. I should set up a trophy wall from my PRU days where this has happened. Once you get bit, then you are forever second guessing and trying to account for the unknown unknowns.
Did you start with a 20x12 art board?
Did you move the design in the GFUI operations space or change it in any way?
If yes for the first question and no for the second question, as long as you don’t move the material in any way, you have a chance of getting it to cut where you want, even after shutting down.
Otherwise, figuring out how to cancel the print and remain in the same GFUI operations space without changing anything might get to where you want to go.
I’m curious as to your trial and error, testing routine for custom and Proofgrade materials. Generally I have two kinds of tests. One that is confined to materials testing so I know what effects the different settings have on the material when departing from Proofgrade settings. The other is testing a design. When I test a larger design, I generally use cardboard just to make sure I am understanding how the design is processed and can adjust accordingly.
Then there is the other situation where you have Proofgrade material and default settings and it still doesn’t work, because of material warp or some type of software/cloud/processing snafu. That is the really bite.
Still thinking of a pre-flight checklist escutcheon that I read through before pressing the hardware print button.