m15 R7, doesn't turn on

Alienware M15 R7 few days ago decided just to not power on, however it doesn't seem to be completely dead.

When laptop is on battery or plugged in the only key which I can turn on/off (it lights up) is the windows lock key.

Another finding that after 20-30 seconds of holding power button while charger is plugged in keyboard becomes lit in rainbow colours, fans starts for 1 second and then turns off, back of the laptop RGB colors turns on (logo and tron) and then power button also shows as charging - however after 15s power button and back of the laptop becomes inactive (but for some reason keyboard is still lit in rainbow colours?).

If I try to recreate the same scenario while only on battery - it doesn't work (I can only light on/off windows key button as mentioned before).

Anyone has ideas what can be wrong here or maybe how to fix it? I already tried holding power button for 30s - 1min multiple times (while battery is disconnected and charger not plugged in), however it didn't help.