Question Gigabyte Z390 Mater G2 power on issue

Dec 12, 2019
Gigabyte Z390 Mater G2 mobo

i9 9900 CPU
32gb 3600 Corsair RAM
2 x Samsung NVME drives
thermal take air cooler
Gigabyte graphics can’t remember the model at the moment, but mobo has on board too
700w PSU

So, I have put all the pc together, connected the 24 pin power connector and 2x4 pin 12V_ATX connector to one of the 12V_ATX connectors on the mobo, I have connected the CPU fan to the CPU fan header (need to check if the pin out is right for this as I just plugged in the plug as it came). Connected 1 sys fan to the SYS_FAN connector on the bottom of the mobo, all the other fans are controlled via a controller in the case.

So the issue is when I press the case on button I get a blink of red lights for around a second then it just switches off, does the same again if I press the on button.

So any tips on how to trouble shoot this?