I thought I had fixed it. But heavy rain on Friday I had it enter the cabin again.

Were sealed to the roof last year, and a broken drain repaired.

What else could it be?

There's only two places water can enter the cab via the sunroof and both have seals, so if they are intact and working then it must to be from some where else, all you can do is sit inside the cab next time it rains, or use a hose pipe, and watch for the drips.
According to other posts, the tops and base of the windscreen or the roof gutter can allow water to pass but that may be a D1.

I've just had a full professional repair done to both sunroofs, by tony from fylde, PM if you want is details, you wouldn't believe the places they can leak, i tried it all, but this guy took a day and it's fantastic, I've had it done over a week now and just left it outside getting hammered by rain, the headlining as been sent off to get relined, it's a great feeling knowing as much as it Peez down Its gonna be dry,