>>BTW, how old is this laptop? If the battery pack is several years old, it could be near the end of its useful life (i.e. its capacity to hold a charge decreases over time, and depending on how you've been using the battery could affect its useful lifespan).
>
>The laptop is 9 years old. A new battery should be delivered today. I can't wait to test it.

Laptops have high-energy battery packs and manufacturers are deathly afraid of fires. A laptop battery will charge only if everything is perfect:

- the battery
- the charger
- the interaction between the battery and the charger i.e. that the battery responds as expected to the charge being applied

If anything looks "off", the laptop will run from utility power (in some models you can even remove the battery completely and run it on mains power), but battery charging will be disabled. Hence the dreaded "plugged in, not charging".

Power outages are often accompanied by spikes. As a result, your charger and/or battery may no longer be "perfect".

John makes an excellent (and unfortunately, expensive :() point about quality of replacement batteries. Although they usually cost twice as much, you're best off with OEM replacements. If you need to go Amazon or eBay, make sure the vendor has been around for a while, has lots of positive reviews, no recent bad reviews, and that the reviews are real (not bot-generated or otherwise fake).