EliteDesk 800 g4 "boot loop"?

[brokenelitedesk]

First time using this forum and to be honest not sure if the EliteDesk is a desktop...

I had Windows 10 Enterprise installed. It worked for 5 minutes at least without any problem. When booting the computer for the first time i spammed f11 to check bios (haven't used this computer before). I ended up in some kind of boot/safe start menu but skipped it and booted into windows everything working. (using a mac keyboard with USB and HDMI to the montior via the "extra port") I then shut the computer down, inserted the windows 10 (not eneterprise) usb install and booted. Spammed esc as I had googled that was the way to BIOS. Ended up booting into the installed version of windows. So I turned it off again and rebooted spamming esc. Since then, black screen. I have tried removing CMOS battery (not finding a reset button), tried booting without ssd, tried another hdmi, tried using DP port instead, tried moving the RAM stick to the other slot. Nothing, no display at all. (booting without any USB stuff etc)

The only signs of life I get is:

Sometimes the power led (white) lights up just as if the computer was working and the fan start spinning right away.

Sometimes the green led (I think hdd) lights up when holding the power button. After tapping and holding randomly the power led also kicks in and the fan starts to spin.

In both cases the fans and leds shut down after 30 sec- 1 min to be dead for a second or two, to then come back to life for a mintue and then die again.

Any tips or solutions? I mentioned mac keyboard in case I need  to press f11 or windows button etc and it might not work with a mac keyboard.