Acer laptop not starting up properly

I have an acer aspire E1-371, my brothers are at uni doing computing so they know what they're doing, we open the laptop and clean the fan section out 1 or 2 times a year as our house builds up a ton of dust. We cleaned it today and took out about half an inch of dust covering the vent, could tell it needed cleaning as the laptop was overheating.

We reassemble just like we've done many times before and when I push the power button there is no display, the fan turns on for a few seconds then stops, all LEDs still work and the power button remains lit.

We've spent the last 5 hours going through every bit of the laptop reconnecting and thinking of possible problems to no avail, I've tried holding the power button method with nothing plugged in, tried plugging into external device and seeing if it will display but it does not.

I am extremely baffled as to what has happened, any help would be greatly appreciated! Can't really afford new laptop right now so that's not much of an option.