Issue that make me want to cry! PC offline /win 10

Hi all 

Sorry if this already has a topic.

I am base in norfolk and have about 120 mini servers (Intel NUCi3) run all over the country.

I have some the are doing the window updates and come back up no problem. I have  others that do not.

All the server have had all the power setting set to always on and are still working I just can not acess them and they show offline.

as soon as you connect a screen, mouse and keyboard they start working again and appear online.

Any thoughts on why this is happening?