XPS 8930, two not turning on

hELLO 

I have three XPS 8930s

They all work splendidly. I had one at home turned on. 

The two other Dells here at the office were off.

I turned one on - nothing happened. I then went to the other computer turned it on nothing happened.

I changed out to using two other monitors - that were connected to pc, and working.

Restarted both Dells' nothing happened.

What I did as is the usual routine pressing an F key was to keep tapping the F key while the computer turned on.

I pressed F1 F2 F8 F9 F10 F12 Esc Del 

On both Dell XPSs - nothing happened. 

I thought using a windows 10 DVD that turning on the computer that the install would run. Nothing happened.

I open the case on both Dells re inserted the memory. Motherboard on both green light active; power supply running, CPU fan running - the usual. 

So I removed from both all memory except one stick Nothing happened. I removed all the memory thinking the computer would give me a Beep code. Nothing happened. 

I pulled the cables from the internal hard drive removed the memory restarted nothing happened.

If it were one XPS that was at issue that would be the challenge to figure out what to do but its that both Dell XPS that were running splendidly before I powered them off - two , two XPS failing complete with an attempt to 'power them up. This is an office environment. I have HP and Dell workstations running in the office - except that on two separate desktops I have two XPS s sitting there - in the state of nothing, happening.

What's to do?