I guess you might flash on dos. if you have refresh on windows base, sometimes, it recover for the information. if it doesn't allowed, like same version, try to force flash on windows base. it is still same. you need to set up DMI setting for the missing serial number. there are hp dmi setting tools from there.
i dont understand any of this refresh on windows base? force flash on windows base? what does it mean? /noob
@ Parachute on HP website it also said Personally I would contact company who replaced your motherboard it is their responsibility you shouldn't need to be flashing bioses e.c.t.