New 8GB Pi 4 does not run headless ?

I have a nice new 8GB Pi 4 which seems good in all respects except that I have not been able to get it to run headless.

A SCSI Drive 4 which boots headless on a range of other Pi systems, wiil not boot headless on this 8GB Pi 4.

5.28 and 5.29 both boot OK with a monitor but not headless.

Does anybody else have a headless 8GB Pi 4.

^{Yes, I know the OS does not support the use of 8GB memory, but this was the only new one I could get. In all other respects, it seems fine and will run with the monitor disconnected after boot, showing 4GB of memory.}

Have you got
hdmi_force_hotplug=1
in your config/txt?

Have you got hdmi_force_hotplug=1 in your config/txt?

Brilliant. Thenk You. I can reboot it remotely, now.