DIAGNOSIS Yes, but you must use the official Ninja Reusable Coffee Pod, not place a loose K-Cup in the basket. The brewer's puncture system is designed for that specific pod.
FIX Get the Ninja Reusable Coffee Pod (model RP1). Fill it with your own ground coffee. When placing it in the single-serve basket, ensure the flat, perforated side faces DOWN. Lock the brew head handle firmly. The brewer's needles will puncture correctly through the designated spots on the reusable pod.
IF THAT DIDN'T WORK If you have the reusable pod and it's still leaking, the silicone seal on the pod lid is likely damaged or missing. Inspect the clear silicone ring on the underside of the green pod lid. Replace the pod if the ring is torn.
HEADS UP Never try to use a standard Keurig-style K-Cup. The puncture pattern and pressure are different, which will cause improper brewing, leaks, and potentially jam the needles. The mess is from water bypassing the coffee grounds entirely.