Laptop rained on, now it won't load OS
So, I did something stupid: I kept my laptop near an open window despite being warned about the possibility of rain. I went out for lunch and when I came back, the top cover of the laptop was covered in rain droplets. I cleaned the water off, turned off the laptop (it was in sleep mode during all this), and then let it dry for 4 days before attempting to turn it on again.
When I did, everything seemed normal. The laptop went through POST, loaded GRUB (I'm running Fedora Linux), and everything worked normally until I input my password: it started loading only to then shut down. Thinking it might have run out of battery, I plugged it in, but the power LED didn't light up. Pressing the power button also did nothing. Only when I replaced the battery did it turn on again. The same thing happened, but this time it shut down after loading the peripheral settings (like volume and screen brightness). Once again, only when the battery was replaced did it turn on again, only to shut down during OS loading.
To check component integrity, I decided to run memtest and hard drive check, and both completed with no issues, despite taking much longer than a normal boot up (this tells me that the issue is probably not with the battery). I finally decided to open the laptop up to check for water damage, but I didn't find any. I unplugged and plugged several cables and the SSD, but to no avail.
The only clue I have as to what might be happening is that after choosing an option in GRUB, an error message pops up saying something like "This OS version [...] it's past its support date" (it pops up too quickly for me to able to read it). Any clues as to what is happening? And what can I do to fix it?