The laptop was new at the end of August 2018.
A few days ago the HP Support Assistant providied a BIOS update which I installed.
Since then on power up I first get the power switch light flashing, then the light on the caps lock button give 3 long and 5 short flashes which I understand says it can't find the CPU.
Forcing a power off, waiting the n powering on again gives "The CMOS checksum is invalid." CMOS 502.
Press enter to rest and the computer starts and runs fine.
I assume that the BIOS updtae is invalid, or has not installed correctly (all done through HP Support assistant).
Any advice and a fix greatly appreciated