No Boot, VGA Error

[jhheinz]

As described in the title, my system will not boot. I have it plugged into a monitor via HDMI, however when I power on the system the motherboard shows the VGA error light, passing CPU and RAM but not getting to Boot. When I unplugged the graphics card from the monitor and powered on the system, it got to the boot stage and then the status LEDs turned off, so I would assume it booted fine. However after plugging in the monitor nothing shows up. I validated the monitor with a different device so that is not the issue. I also tried reseating the GPU, to no avail. This is such a strange problem I just don't know where to start so thanks for any help. Full specs below:

 

SPECS:

Ryzen 5 2600

Gigabyte B450 Aorus Pro WiFi

Corsair Vengeance RGB 16GB DDR4-3000

Kingston A400 120GB SSD

Seagate BarraCuda 1TB 7200RPM HDD

Gigabyte Radeon RX 580 GV-RX580GAMING-8GD 

Corsair SPEC-05 Case

Corsair CXM 450W 80+ Bronze PSU