If I'm understanding correctly; yes, I had the same problem with my porch. It would leak in the basement where the porch slab meets the house.
On the porch, I removed the bottom row of vinyl siding & starter strip, applied a healthy bead of silicon into the seam, took some aluminum flashing and pressed into the seam and then reapplied the vinyl siding over top of the flashing. Haven't had a problem since.
Oh, welcome to the site & good luck with your repairs.