The car will not power on after leaving the sunroof open and it rained?

Yep, electronics do not like that at all. Can you please upload a video of what's going on so I can see? Do any lights come on? We need more information to help you. From what I can see the BCM may have got wet. We should run a CAN scan to see which codes come up to be sure that is the problem. You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

Here is the location of the BCM so you can check it out. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.