We need more information. This is most likely a setting in your motherboard's BIOS Setup Menu and not a problem with your card.
For some ASUS boards, in the BIOS Setup Menu under the BOOT menu there is an option called "CSM" (Compatibility Support Module). This is Enabled by default. Changing this to "Auto" typically fixes this issue, though you may have to try "Disabled". For some Gigabyte boards, the options are Enabled and Disabled only (no Auto).
Of course this a Catch-22 issue. You need to see the BIOS Setup Menu so you can change a setting in the BIOS Setup Menu. But you can't see the menu to make the change. So you may have to change to VGA or Display port instead of HDMI just to make this change. That may even mean temporarily swapping in a different monitor.
Also, when you install a card, if your board supported integrated (On-board) graphics, the integrated graphics is supposed to disable itself. If yours didn't, or you manually enabled it, there should be setting in the BIOS Setup Menu to set the Initial Display Output to the PCIe slot. You don't normally have to change this but it might be worth a try.