I had a sunroof leak In our XC70

I taped all around the sunroof with high quality duct tape that was much more flexible than regular duct tape - I am sure that the sunroof was sealed - still had a leak.

My tech found a leak at the top of the windshield - I let them bring in a windshield company - they broke my windshield and - I still had a leak

If you find or suspect a windshield leak at the top, try some tape first - Use three strips of ordinary electrical tape - take care to let it relax, as you stretch it when you take it off its roll. Clean above and below the windshield groove and run one strip above the groove to give a good surface for the next strip which you run over the groove, then run a third strip lapping over the second strip to serve to block the wind at speed.

When we owned 850s, they were known to lose their rubber strips across the top of the windshields - I sealed the rubber strip (after I lost two!) with two strips of regular electrical tape - this fix lasted for years.

A tech cleared the drains = I still had a leak

Did I mention that in a bad rain I had 2 INCHES OF WATER ON THE FLOOR!

Once more they cleared the drains, finally the leak has stopped. (Personally, I think that they found another back-up somewhere.)

Claus posted that sometimes the drain hose can break or split in the door post - perhaps you should look there.

I suggest -
1 check your windshield
2 Tape your sunroof
3 Remove trim and check your drain hoses

Good Luck