First try doing a powercycle. Remove your Power and hold the power button down for 30 seconds. Attach the power and try booting. If you have access to the CMOS battery I would remove that first and then do the powercycle. Then attach the CMOS battery and boot.
I extracted the BIOS files for this Envy and it looks like the HP flash is only available for Windows. Some HP BIO's allow you to create a flash drive that is attached to the computer. Booting the computer reflashes the BIOS but this is not the case with the BIOS for your envy. There are BIOS flash tools for the AMI Aptio that allow one to flash in DOS but I can't say this would work on an all in one.
This is using DOS and you have the newer UEFI instead of a legacy BIOS. I do not know what will happen using the DOS version of the AMI flash program and if this bricks the computer I take no responsibility. Read the PDF in the AFUDOS.zip file.
Extract the BIOS SP file using WinRar or 7 zip to get your ROM file. Use the ROM file with Rufus which makes a bootable flash drive using FreeDos. Select FreeDos in the dropdown box that lists iso image. Copy the ROM (LA3_816.ROM) from the extracted BIOS file to the root of your flash drive after using Rufus. Copy the extracted AMI Aptio AFUDos flash files to the flash drive. Boot the Flash drive. You may need to change drive letters and then using the DIR dos command to see if your ROM file and the AMI flash files are listed. Use the command in the below AFUDOS.exe link to flash the BIOS.
https://www.bios-mods.com/downloads/ Look for AFU for Aptio v2.28
If you need any help with the DOS commands after booting the flash drive with freeDOS post them but I would highly recommend you contact HP support before attempting this flash.
A youtuber was able to fix a corrupted BIOS on an Envy 23 using a USB programmer but I don't have any experiences with using one of these programmers. There are numerous articles and videos on the internet regarding their use.