Turning off 'fast startup' in power settings was the usual fix.
What OS ?
Don't know why you can access from vga, but not hdmi (unless it's because you power off to swap cable/port).
Ill have to login to my bios with my gigabytes motherboard. Is the fast startup located in bios? My os is dual boot between windows 7 and 10. I got both connected to the ati card the vga cord and hdmi and I gotta unplug hdmi from the monitor and plug in the vga to the port on my monitor then i gotta select vga and reboot to access bios. I only turn off the screen as i change cables on it as the computer is still running.
I disabled the win 10 fast start up and did not help. I know when its in bios but when using hdmi biso screen is black. I cannot take the cmos its behind alot of stuff in my case starting with the graphics card is like blocking to get it it easy. My computer is custom built. So getting the cmos i would gotta take out some stuff to get to it so cmos removal not a option.
fast-boot of your BIOS/MoBo is more important (than MS fast-boot) here...
if you dont do a cmos WE CANT HELP YOU!https://www.ebay.de/itm/40X-2-54MM-Breadboard-Dupont-Jump-Wire-Stecker-auf-Stecker-Jumper-Kabel-10-30cm/372273371526?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
usually there are 2 pins that have to be shorted - and usually they are placed easy(ish) to reach
some better boards already have a cmos-button
AND when you found those 2 pins you could simply use: 40X 2.54MM Breadboard Dupont Jump Wire Stecker auf Stecker Jumper Kabel 10-30cm | eBay // jump wire "female to male" and buy a jumper to short them when ever you need to...