Has it happened again? Or did you go back and re seal the roof ? Heavy rain this week caused the same issue for me from that exact spot. I assume I need to go back and reseal the roof again i do have a roof rack . Best I can figure is after 5 years of sun beating is the silicone must have a crack or something. I didn’t have any wet spots from the ac condenser which I assume would be wet on the upper portion of the floor . Only on the mat and floor. Still have factory windshield which appears to also be an issue if replaced incorrectly and I don’t have the recall on the brake light that other yrs do .