Pretty sure the psu in this AIO unit is stopping it powering on for more than 3 seconds.
Hopefully someone has one laying around in the workshop and can spare it.
Ok... pulled the unit and psu apart, and all looks and tests fine.
The AIO came up with an LED sequence at one point, or 2 flashes and then 3, which by my reading of the info out there speaks to a fault with either the CPU or Motherboard.
Anyone have a board that will take an i7-7700 cpu and happy to test the cpu?
Drop me a line please if you do, and I'll get it to you.
I've got a B250 sitting around that I could try it in.
PM me! :-)