Emergency BIOS recovery does not work

[MarvinDavis]

While attempting to upgrade my HP 15-bs115dx to the latest BIOS, I seem to have corrupted the existing BIOS.  When I turn on power the fan starts, an internal LED lights up, and there sounds like there is some disk activity, but the screen remains black, as does an external HDMI display that I tried.  The problem started immediately after closely following BIOS upgrade instructions.   Old, working BIOS was F.33  Released 12/8/2017.  New, attempted BIOS is F.71 Rev A released 11/28/2022.  F.71 was selected after I entered Win 10 x64 as my O.S., even thought my O.S. was Win 11, since Win 11 was not an option but had been working fine with F.33.  The BIOS upgrade was attempted because I had planned on installing a M2 SATA drive and thought having the latest BIOS was a good idea.

I have tried "everything"... Power ON with no power present.  CMOS battery reset.  ESC after power on; F2, F10, F11 after power on.  I have attempted the documented BIOS recovery sequences many, many times, with both upper and lower case letters, namely Win+B, Win+V, B pressed and held just before power on, sometimes holding keys for 2 minutes, sometimes releasing soon after Power-on.  None of this has had any effect.  I have tried with the single SATA HD removed (since it has WIn 11 on it).... thinking this BIOS should be recovered and then complain about no boot drive. But nothing.  

I have never heard any beeps, only the fan and disk activity (when present, of course.)  I have tried the Windows key method with no USB's installed and with a "recovery USB" containing the new F.71 BIOS.  I was unable to find the older BIOS, F.33, on your web site.  

On this forum I have found references to documents that may help, but they have been deleted or archived.

Help!