Computer not fully booting - no signal to monitor

So a couple of days ago when I started my computer it got stuck in a booting screen (black window with a blipping underscore in the upper left corner). I held the power button for a few sec until it turned off and when I tried to reboot it it got stuck in some boot-loop where it was on for 5-10 seconds, then it turned off and then turned on after a few seconds and then off again etc.

To solve this boot-loop I had to reset/jump (or whatever you prefer to call it) the cmos - by doing this I got out of the boot-loop but now my monitor doesn’t get any signal (which it didn’t in the boot-loop either)

I have tried
Removing the power cord and holding down the power button for about a minute

Removing and reconnecting the RAM

Booting with only one RAM (in the correct socket)

Reset the cmos

Changed battery for cmos

Booting with a different graphics card

Tried different monitors

None of this solved the problem and I still doesn’t get any signal for my monitor.
All the fans are running and all the LEDs on the motherboard etc is lit, so I don’t believe it’s my PSU causing the problem.

Now I’m pretty much out of ideas, so I’m very grateful for all the help I can get!