It sounds like you’ve done the basic stuff already. Check the door drains too. Each door has a bevy of holes at the bottom, a little awkward to get at though. Sometimes these holes are easier to see w/a mirror. Make sure they are not clogged. The other common place for rain to get in is the rear tail-lights. So check for dampness on the floors back there too. If there’s a well for the spare tire, look for water accumulating there also. Those rear hatches can cause leaks, often due to an incontinent seal at the top.
I had this problem on my truck and it was caused by water entering three places. (1) Water coming off the windshield was entering the under-windshield drain system ok, but diverting to the interior b/c the drain system was clogged up with leaves and sticks. (2) Small leaks due to cracks in the windshield/flange gasket. (3) Water from roof wasn’t making it all the way to the ground through the roof drain system. De-clogging all those drains was a big messy job, but I eventually got it flowing freely again.
On my Corolla I had some water getting in due to a tail-light leak, after I replaced that tail light. I had to re-seal it.