Open The Roof. Find The Drain Hole In The Corner Of The Opening Nearest The Leak.
Slowly, Carefully, Begin Pouring A Little Water Into The Drain.
Keep Checking Headliner For Wetness And Drips Of Water Under The Car.
Wet Headliner = One Of The Problems In The Bulletin.
Dry Headliner & Water On Ground = The Problem Is Probably Something Else.
Sunroofs are not designed to seal out all water when closed. Therefore drains are built into the corners of the sunroof opening to drain away any water that gets by the closed roof. They must function properly or water will enter the passenger compartment, someplace.
Also, I'd pull up any mats on the floor nearest the leak and at the lowest point of the floor, press my hand into the carpet and feel for moisture. The floor should be bone dry.
I would think the leaking will leave a stained headliner. Have they metioned warranty covering its replacement ? Be careful, though. Few people can properly install a headliner, correctly. The cure could be worse than the stain problem. Trim shops are usually best at installing these.
Also, a leak of this nature can start causing problems with electrical wiring and connectors. There is a chance that you've even got wiring near the water stain. A dealer needs to figure this out soon.