Battery will not hold charge, drains while plugged in

[rippertear]

Yesterday I noticed my HP ENVY x360 m6 laptop is no longer charging properly. The battery does not charge while plugged in, whether the laptop is on or off. It is also slowly draining on its own- not as quickly as it usually would, but it has dropped roughly 15% of capacity in the last 12 hours, during which it was continuously plugged in. I first noticed something was off last night- It had been plugged in continuously for several days (I don't move it much), and the battery was somewhere around 60%. I turned it off and left it plugged in to charge overnight, and when I turned it on this morning, it had not charged. It is evening as I write this, and the charge is now at 40%. 

It does not shut down if unplugged, nor do anything but dim the screen slightly. Everything seems to behave as I would expect it to, other than the battery failing to charge. 

The power icon in the lower corner shows a plug, and it does display as "Plugged in", but the bar for the battery does not move as it does when it is charging, and it does not say that it is "Plugged in, Charging" as I thought it used to.

I have looked through the other posts on this forum and tried a few things, as follows:

Neither the pin in the charger nor the computer was bent, damaged, or obstructed in any way. I've also tried various different power outlets, and even a different charger, to no avail.

I've updated the BIOS and all of my drivers through the HP Support Assistant, as well as the download-and-run updaters through the support.hp.com website. I've also done any pending Windows updates, which made no difference.

I've deleted the battery and power supply drivers and reinstalled them, to no discernable change.

I've checked the battery and AC Adapter through both HP Hardware Diagnostics and HP PC Hardware Diagnostics UEFI. They passed every test, and both the "Fast" and "Quick" system checks in the HP PC Hardware Diagnostics UEFI showed nothing wrong.

I've changed the power plan to the Windows default, to no effect.

I can't recall anything that would have caused this other than uninstalling the Candy Crush game that was installed automatically on this laptop. I didn't strictly have any reason to, but I really, really didn't expect that to be crucial to the ability of this laptop to function. I don't expect it did, since if the rate the battery is depleting is constant, then it started a good while before I deleted it. I only mention it because that is the only significant hardware or software change I can recall making in the recent past, and that seems to be a standard question, so I thought I should mention it.

As I understand it, all of this is either indicating nothing is wrong or should have fixed the problem. This laptop is at least four years old, but it was purchased new and has been taken good care of. Is there anything else I can do?

[rippertear]

Update: after posting last night, I turned the laptop in question off to conserve charge. It was around 40% at that point. This morning, I turned it on to see the battery had reduced to 20%. However, over the course of the day today, it has only dropped to 19%, so the battery decay seems to at least be slowing? Also, it seems to last much longer when in sleep mode than it does when turned off.

[rippertear]

Update: This morning, the battery was at 11%. I decided to see if it would still run after the battery reached zero. I turned the brightness all the way up and opened a bunch of tabs to try and drain the power as quickly as I could. It then charged up to 13%, then began decreasing again. Now, it is at 10%.

[rippertear]

Update: Last night the battery drained to 5% and then shut off. I bought a replacement battery to see if that would help at all. After installing that today, it has started to charge and has increased from 60% to 81% in less than an hour.

Thank you anyways.

[rippertear]

Update: Until now, my new battery has been working well. However, I've just noticed now that the new battery is only at 95% charged. It has been plugged in all day, and its charge has not increased. Clearly, the battery was not the only thing at fault.

[rippertear · Accepted solution]

Update: after posting last night, I turned the laptop off, and left it plugged in. Just a moment ago, I turned it back on, and saw the battery at 95% still. I decided to try and calibrate it, and began to do so; however, I came to the prompt to either run the hard drive check once or repeat until an error is found, and did not recall which I should do. After cancelling this test and reopening my computer, it is now charged at 100%. I am assuming it was some sort of strange display error, and am remarking this post as solved. 

Edit: After attempting to calibrate my battery, but deciding to stop it for the night and then resume it in the morning, I found that it is in fact failing to charge, after all. Current battery is at 61%, plugged in but not charging.

Edit: After turning the computer off until morning, and turning it on just now, it is charged to 100%. 😐