Volvo xc40 water in boot 100% fix.
This problem occurs in all vehicles that are 4 years old and older. To solve the problem, you need to siliconize with black wurt for windshields two air vents under the bumper on left and right side. I had the same problem on Golf VII 2018, Audi A3 2019 and many other cars..Check out the video how to remove the bumper and picture how to siliconize the air filler.