I cleaned my PC, and when I put everything back together, my monitor had no signal. What do I do?

I just cleaned my PC in the inside and outside, no water was used, just a vacuum and a brush. I removed BOTH RAMs to brush them and put them back as intended. When I turned the PC back on, the monitor said "no signal" and it refuses to show anything.

I've tried restarting the PC, I've tried unplugging both the power and HDMI cable and plugging them back, I've tried switching from my GPU port to video card port, nothing. What do I do here?