Not enough spark, faulty primer, bullet not seated all the way, plugged nipple, moisture could be a few problems. Did it happen more than once? Was it at the end of your range session?

You said cap are you using number 10 caps or mags or 209 primers? I haven' t had a hang fire with T7 and 209' s but have heard others say they have with other ignition types. I actually though T7 requires 209, is this not the case? Not familar with the disc rifles, so I appologize if these above question are N/A.

Clean her out good and give her a go again. Good Luck