Help with PC please. Not booting.

Details:
-shut off weird last night. The fans continued to run, but the screen was black. I waited a few minutes before forcing a shut down by holding the power button down.(I was tired so I just went to bed after that.)
-Woke up. Turned on the computer. Fans started blowing like normal, but it wasn't booting anything. Same black screen as yesterday.
-Check monitor, it says it's getting no signal. However, plugging the monitor in makes it react by looking for a signal. Showing that it's getting power at the least.
-Keyboard must be receiving power, because the light turns on.
-Drawing tablet flashes a light for a second before going blank. So it must be receiving power. Going blank when it doesn't detect a signal.
-I plugged in my phone, and it doesn't bring up any options like normal. Rather, it only receives a charge

So I'm fairly certain most components are receiving power, if not all.

Here are some things I tried:
-Reseated the ram a few times
-Tried both ram sticks individually.
-Changed slots for ram.
-Reseated the gpu
-Reseated the SSD
-Unplugged everything save for the monitor and power cord.
-I fiddled with some connects, to make sure they're in all the way. Though admittedly, I haven't tried them all.

I didn't reseat the CPU, because the way it's connected is strange. I never saw that kind of component before. It's round with a circular piece of glass. And I don't have any thermal paste, so if I undo the paste by mistake, I won't be able to put it back properly.

I don't see any lights on the motherboard.
There is no beep when the PC is turned on.
Because the monitor doesn't receive a signal, I can't tell if it's actually doing anything. However, since my phone doesn't attempt to connect to the PC beyond charging, I'm inclined to believe that it hasn't booted windows.