My old HP Pavilion gaming laptop 15-ak049tx kept displaying bootup error "CMOS Reset (502) The CMOS checksum is invalid". Another symptom is the Windows Time/Date is always off.
It is likely that the CMOS battery is flat.
You should download the "HP Pavilion Gaming Notebook - Maintenance and Service Guide.pdf" guide from the official HP website, I followed the guide to remove all the screws. I'm using an old computer screwdriver set "JK-6089-A" that I bought from Challenger many years ago.
But I still cannot pry open the cover, I kept at it not knowing if I should pry it as hard as possible - until I found two hidden screws (cover by stickers). Remove these hidden screws, and it should be "easy" to pry it out, with a small flat screw driver.
The HP Pavilion 15-ak049tx uses a CR2032 3V battery, luckily I had one spare. I bought a few to power my Red-Dot sight years ago from Shopee. It seem to still work.
