My HP 15-r031ds Notebook PC cannot boot, blank screen, caps light blinks every 3 seconds, no beeps

[Kbh-39]

On February 14, 2025, my HP 12 Notebook PC started failing to boot into the operating system. This was signaled by the screen remaining off and the caps lock light blinking once every 3 seconds. Though I was soon able to successfully boot into the operating system the first few days, it became harder and harder to do so, and as of today (February 18, 2025), it cannot boot at all. I looked up the caps lock beep code, and it said the CPU is not functional. When I first noticed this problem, I tried everything I could think of to diagnose the issue, including using command prompt, Windows Memory Diagnostic to check for possible memory errors, Disk Management to check the health of my hard drives, and HP PC Hardware Diagnostics Tool to perform a System Fast Test; everything indicated that there was no apparent issue. I later entered the BIOS setup utility to see if there were any error codes in the system logs, and the one I saw was the code 0601 with a time of 011321-053242, which indicated a problem with the primary internal battery. But before I could exit the BIOS, the computer locked up and none of the commands could be used, so I had no choice but to force shut down the laptop by holding the power button. After that, I could no longer boot into the computer, even though I made no changes to the BIOS. The internal fans have also stopped working and will no longer power on, possibly meaning the processor is not functioning. I've tried performing a hard reset by unplugging the adapter, holding down the power button for 30 seconds, then re-plugging the adapter in and powering the laptop on, nothing happens. Also tried repeatedly pressing the escape button immediately after turning the laptop on, and holding the windows button + B and holding down the power button for 2-3 seconds to try to access the BIOS settings; this does not work either. The laptop can receive power (the ac adapter LED and f12 LED both light, and the green light from the DVD drive flashes, but the processor does not start. No beep code can be heard either, since the BIOS can't perform a power on self-test. A few prior days I attempted to boot into the operating system, the laptop would either display nothing or power on the screen (which remained black), sometimes with the fan spinning. My laptop is a retired product, and no more updates and drivers are available for it on the HP website. I'm not sure whether the CPU is dead, the motherboard is malfunctioning, or if the RAM or BIOS is having issues, but I think there is an issue with the CMOS battery. Can anyone please help me solve this sudden issue? The warranty has long since expired and I'm not confident in opening up the laptop myself to see if anything is wrong.

Not sure if this is related, but a few years back, my removeable battery (in the back of the laptop) started not to hold a charge, so I started relying solely on the AC adapter, meaning I had to leave the laptop plugged in to use it. Occasionally after that, my laptop would abruptly turn off on its own due to a "thermal event" listed in the Event Viewer. Here is all the information about my system that could be useful.

Also a description of two separate BIOS errors listed in Event Viewer.