Resetting a BIOS password on an HP EliteBook 840 G7 is significantly more complex than on older models. Due to enhanced security features, there is no "master password" or simple jumper bypass.
Turn the computer back on. If successful, the unit restarts and may show a "CMOS Reset" screen. Plug in the AC adapter. Press and hold the Windows key + V . hp elitebook 840 g7 bios password reset
You need the board schematic (available on repair sites for a fee). Without it, do not attempt. Resetting a BIOS password on an HP EliteBook
If the above methods don't work, you can contact HP support for assistance. They may be able to provide you with a master password or guide you through the process of resetting the BIOS password. If successful, the unit restarts and may show
Buying a pre-programmed BIOS chip for the 840 G7 and soldering it onto the motherboard is another alternative mentioned by technicians. How to Reset HP Elitebook Administrator and BIOS Passwords