Hello, I am a complete novice with computer hardware so I hope I'll be able to explain things well.

I've recently had problems with my desktop's system fan so we opened up the computer and removed the fan. We didn't do anything and placed it back in afterwards but now when it turns on, the computer will power on fine, no beeps to be heard and with the fans running, but the monitor does nothing. If I press the power button on the monitor it will say "no signal" and then go back to sleep. I've also noticed that the light usually present on the bottom of the mouse doesn't turn on, but it will turn on and work fine when connected to my laptop.
The monitor is connected by a VGA cable but also has input for a DVI cable, and during the brief moments the monitor is on, it says that the default signal is DVI, but I'm not sure if this part of the problem.
I'm open to any help and ready to elaborate as best as I can if needed.

Thank You!!!

I didn't find the right solution from the Internet.
References
https://www.cnet.com/forums/discussions/monitor-says-no-signal-1/
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