Why do i keep getting message saying CHOS checksum is invalid and computer will not start

[carolemarg]

I put my computer on 3 days ago and had this message on the screen  The CMOS checksum is invalid.The CMOS will restart to the default configuration,and the computer will restart. Afterwards pleas check the BIOS setup options to see if they change. CMOS Reset (502).Enter-Restart computer. I  do not understand ant of this .  When i do get the computer started after turning it off and on it has gone back to the time i turned it off the night before.    The computer is HP PAV 15/8GBOPT.   [Personal Information Removed].   I hope you can help me on this matter .Thanking you  Carole.

[WAWood]

Here's a link to an HP document about CMOS error codes:

https://support.hp.com/us-en/document/ish_4209641-3226345-16