Why won't my laptop turn on?

My laptop won’t turn on and I’m wondering whether it can be easily fixed.

I have an HP Elitebook 840 G6. I got it about 2 years ago. I have been using it a lot. Up until now, it has been working perfectly.
I left it off and unplugged for about 5 days. Now it won’t turn on. When I press the power button, pretty much nothing happens (see below). Any ideas?

I tried some different stuff without really doing the appropriate research (see below); I’m probably being a massive idiot and unknowingly frying my computer. Feel free to let me know if so.
Here are some things that I have observed (mostly very obvious things):

- The laptop has a cylindrical “normal” charge port and a usb-c port. I think that that usb-c port can also be used for charging, but I have not tried that before now. There is also a light next to the charge port which I will call the “charging light”; a light on the power button which I will call the “power light”; a light on the caps lock key which I will call the “caps lock light”; and a light on the left side of the laptop near the user which I will call the “unknown light.” The “uknown” light is in a group of three lights and I’m not sure what it’s for. I have two power cords that plug into the “normal” charge port, which I will call “power cord 1” and “power cord 2.” Both cords are working with another laptop.

- Here is what happens under some different conditions:
1. With a USB-C charging cable plugged in, no other power cords plugged in, and the battery removed: Right after plugging in the cable, the caps lock light comes on and stays on for a few seconds, the unknown light blinks on and off once, and the charging light blinks alternately white and orange a bunch of times. A few seconds later, the charging light turns orange and stays on indefinitely. Pressing or holding the power button doesn’t do anything.
2. With a USB-C charging cable plugged in, no other power cords plugged in, and the battery connected: After a few seconds, the charging light turns orange and stays on indefinitely. Pressing or holding the power button doesn’t do anything.
3. With power cord 1 plugged in, no other power cords plugged in, and the battery removed: The caps lock light comes on and stays on for a few seconds the unknown light blinks on and off once, and the charging light blinks alternately white and orange a bunch of times (just like scenario #1). The power light flashes on and off once (unlike scenario #1). Then there is a short pause. This sequence repeats over and over (unlike scenario #1).
4. With power cord 1 plugged in, no other power cords plugged in, and the battery connected: A few seconds after plugging in the cable, the the charging light blinks alternately white and off a bunch of times. Pressing or holding the power button doesn’t do anything.
5. With power cord 2 plugged in: Same as with power cord 1.
6. With no power cord plugged in and the battery removed: No lights. Pressing or holding the power button doesn’t do anything. Connecting the battery causes a light to flash (I think it is the unknown light).
7. With no power cord plugged in and the battery connected: No lights. Pressing or holding the power button doesn’t do anything, unless I hold the power button down for a long time (seems like 60 seconds). If I hold the power button down for a long time and then let go, the power light flashes and and then off, and the caps lock light comes on and stays on for a few seconds.

- Before trying the above scenarios, I did the following in order:
1. charged the battery for 8 hours with power cord 1;
2. tried plugging in the laptop and turning it on normally;
3. charged the battery for 2 hours with a USB-C charging cable;
4. held down the power button for about 60 seconds with the charging cords unplugged and the battery connected;
5. held down the power button for about 60 seconds with the charging cords unplugged and the battery disconnected.
6. I don’t think those things changed anything, because I tried some of those scenarios before the charging/power button stuff and got the same results.