OctoPi wont boot up

What is the problem?
I flashed the OctoPi image onto my Raspberry Pi 3 B+, using both Etcher and Win32. I then put in my network settings according to the directions. However, when I plug the Pi onto power, it does not connect to the network. When I connected it to my monitor via HDMI, nothing started, so the OS itself is not booting. I am a beginner to 3D Printing and Linux, so please keep the explanations simple.

What did you already try to solve it?
I have tried 2 different SD cards. I have formatted it using both the default Windows utility and SD Card Formatter. I have flashed the image using 2 different softwares.

Additional information about your setup (OctoPrint version, OctoPi version, printer, firmware, octoprint.log, serial.log or output on terminal tab, ...)

Share your octopi-wpa-supplicant.txt file contents, redacting your password.