11-16-2019 07:16 PM
I *think* the mainboard is telling you it has a power failure.
Verify that the AC adapter you're using is the CORRECT wattage for your All-in-One.
Newer HP All-in-One's will give you POST beeps if the AC adapter has a lower wattage than it's expecting.
If you can reply with the exact model you have I'll tell you the wattage PSU you should be using.
11-16-2019 07:23 PM
Welcome to the forum.
I am not a HP employee.
BIOS eror codes for HP PCs can be reviewed at this site (Link).
A 3:4 BIOS error code means you have a hardware problem if your PC was made in 2015 or later.
Possible hardware issues:
Contact HP (Link) if in warranty. Find a good, local, PC tech if you are not in warranty.