I agree, check your roll-paper settings to make sure the cutter is set.
Sometimes when I switch over from sheet to roll, the autocut is disabled and I simply run the cutter from the control panel.
Regarding durability of the rotary cutter and canvas, I printed perhaps a thousand canvas prints in the past couple of years with my second-hand 9900 (the auto cutter for canvas was the main reason for purchase). I can tell you from experience that it's still doing a great job cutting both paper and canvas. In addition to the canvas, I've probably printed several hundred prints. So far, no issues with a dull cutter. Unless you are running the printer night and day for weeks on end printing canvas don't worry about dulling the cutter!