Not sure how I get this message
ERROR: Printer is short of material! Continue?
I have a large roll of pla attached, how does the printer know about material?
In the maintenance section of the Cetus slicer you can input the weight of the filament roll (1000g for a standard roll of PLA) and as it estimates how much material it will use as it prints it will deduct this from the figure you input. I believe that when the Cetus arrives it is setup with 50g input (for the samples that were shipped with the units) and you most probably have used up that amount. Just go in and input the new amount and confirm it.
Or just enter 9999 and the problem goes away for a long time! The measurement doesnt work properly anyway unless you reweigh the spool after every print. Failed or stopped prints count the full amount offilament as being used.