I am a newbie to HA and setup HA on RP4 without issue but when I moved the Pi to a new location where there was no monitor or mouse connected it failed to appear. After much testing it seems it will boot without a monitor connected but WILL NOT BOOT if it does not detected the Keyboard/mouse USB dongle!!!
Does anyone know of a setting that can be changed to get around this issue? I have not found a solution in the forums or on any other site.
Hi,
Installing HAOS in a RPi is usually very simple and just works, so there is something else going on here.
Which RPi3 really matters. The HASS installation instructions call this out as the RPi3a a different beast from the RPi3b.
HASOS has a realistic minimum requirement of 1Gb of RAM, and really needs 2Gb+. The RPi3A+ only has 512Mb of RAM, and although the RPi3b+ works (and is ARM64), it is still a little underpowered for complex add-ons and ESPhome compiles.
Beyond that, experience with hardware and RPi might suggest an odd PSU issue - although it’s more plausible that a duff gound connection might bleed via an HDMI connection than a keyboard / mouse. Over-voltage PSU, and needs more of a load?
There shouldn’t be any Press Any Key To Continue issues in HAOS! 
The usual issue is networking when the installer tries to download the HAOS docker image from GitHub, and it fails, disk breaks, or times out.
I’d usually say posting screenshots is discouraged as it makes offering support very hard, but in this case, you might struggle to get the text logs off the RPi3*.
If this helps, 
this post!
Apologies, mine is a Rasberry Pi 4 Model B with 8GB RAM and has an ethernet connection to the router. I noticed it switches itself off after a couple of days of no activity and needs to be switched back on, then It does not complete the boot and cannot be accessed remotely… very frustrating