2006 V6 Cayenne 100k mi.

My car died at the train station but my son was able to jump start me. I drove the car home and it hasn’t started since. That was May. I did a lot of reading on the forum and I pulled up the drivers carpet and the padding was wet, so I unwrapped the wire bundle, opened all the doors and windows, disconnected the battery, hung the carpet from the steering wheel and let Mother Nature dry the car out.
The ends of the spliced wires were heavily corroded so I cut them back a little and rejoined them. After doing the wires my brake proportioning and lock fault messages disappeared. The lights, radio, a/c all work, but I hear nothing else- silence from my dead car. I checked all the fuses- right and left sides, and under the hood. The ground connection is fine. The 5A fuse under the driver seat is fine as well.
The car didn’t start so I hooked up the Durametric:
Vehicle Electrical System- 907 fault.
Gateway- 532, 1314, 1321
So, I pulled the battery and the parts store exchanged it because it had a dead cell. It was getting dark out, and dinner was getting cold, but I put the battery in place and connected the cables. Lights, radio, a/c all work, but car still doesn’t start. No bad starter sounds, nothing. I can shift into neutral like normal.
I wanted to test relay 433 under the seat but can’t figure out how to remove it without breaking the holder.
I cleaned up the cowl area and the drains are now clearer, checked my A/C drain and it’s clear. The passenger front sunroof drain has some water in it and I cannot pass a line from my weed trimmer/whacked all the way through- I took off the wheel and removed the wheel liner for full access. I tried sucking out any blockage with my shop vac to no avail.

I went in and cut back the wires another 2-2.5” and reconnected them. The floor on the passenger side was dry, and the wires were all intact.
whenever I work on electrical I disconnect the battery. The jump start to the battery was vis the connections under the hood, and the car ran fine on the way home.

Weed-wacker string won't go through the drains. There are two right angles in the drain down near the fuse box at the end of the dash. If you remove the fuse box cover you can probably see them. They're also ones that like to blow apart if you use compressed air and there is a good blockage down below them. Are you certain the sunroof drains are blocked? I tested mine on the 955 every so often by pouring a few ounces of water into the corner of the opening for the sunroof (where the drain is located..) and waited for it to dribble out the bottom.

Twisted the strands together and than shrink wrap over them.

Water is not draining from the front passenger corner sunroof drain. When I pulled the weed whacker/trimmer string outit was very wet after it hadn’t rained in days.
I’m still trying to figure our how water got into the driver footpan.

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Thank you for your replies, I will brush up on my old soldering skills.
is there a way to check continuity after the wires have been soldered together – meaning, checking continuity through the insulation on the wire? The only way I’ve checked for continuity in the past is from one end of a wire and to another,
i’m concerned how far up under the insation of the wire the water traveled and corroded the black wires.