Newly Built PC only outputs when connected to motherboard

[smush]

Hi
Built a new PC with specs:
Motherboard = Gigabyte Z170MX
GPU = MSI R9 390X
PSU = XFX Black Edition 850W Modular
CPU = Intel i7 6700K
RAM = 2x8GB DDR4
DVDRW
HDD 4TB
SSD 250GB

Connected it all up to PSU, put HDMI into GPU turned PC on - the GPU MSI logo lights up but monitor is blank I unplug the HDMI and monitor reads "cable unplugged" I plug it into the motherboard HDMI port and monitor works - I can access BIOS etc. Can anyone help? Thanks

[pastymuncher]

Have you tried setting the pci-e to primary vga in the bios?

[EndlessWaves]

Take the graphics card out, disconnect both power connectors and then re-assemble if you haven't already.

[Bonebreaker777]

Should be automatically via the PCIe GPU but I would suggest the same thing as 'muncher'.

Specify the output to make any PCIe solution the primary.

[VinoVelupillai]

i have had alot of customers that swap their display cable while the pc is running. just shut down ur pc. change ur DVi cable or what ever you are using to your graphics card and than do a reboot.