Have you switched it to use onboard graphics as primary display device in the bios?
Mobo: ASRock H81 PRO BTC R2.0 S1150 Intel H81
GPU's: 6x Sapphire RX570 Nitro+ 8GB
I never had any problems booting the system before as I was setting the rig up whilst the screen was always plugged in and now when everything is set up I must plug the monitor in to boot the system. Never ever had this kind of problem with any other computer systems.
Mainboard Bios -> advanced settings -> disable render stand by.
I'm not sure which suggestion helped more as when I entered BIOS I have change switched on together. Now it boots perfectly from the first time. Thank you!
Good to hear. I've tried the first suggestion on my vega 56 rig and it didn't work for me. This weekend I'll look for the render standby setting . I'm using a different board, so hopefully I actually have that setting.