Don't know whole lot about modern cars, here's what I do on my classics. Determine if water is coming in under use, or when sitting. Blast car with hose, keep hood closed, spray around windshield top first, than side post, no leaks, than blast top of cowl. No leaks, than suspect heater box, open hood and blast heater box. No leaks, than jack car up, and blast wheel opening.
By confining tests to specific areas, problem should reveal itself.
If all else fails, use dish detergent and soap everything up, than gently moisten with hose set for soft spray. Now take an air hose, and blast from inside, trouble area will foam like a mad dog.