MacBook sleeps when unplugged. Battery not recognized by coconut.

I purchased a battery from iFixit in March 2022 for my Macbook Air 2017 i5.  

I installed it, and at first it was working great. Then about 1 month ago, the system stopped recognizing the battery.  When I unplug the power adapter, the computer goes into some kind of sleep or hibernate mode.

CoconutBattery says it doesn't even see any battery.  See https://imgur.com/a/MhSTYXe

Oddly enough, I think the battery is actually charging, and sort of being used. When I plug in the power adapter, it shows green for a moment then goes steady on orange.  And when I unplug the magsafe power adapter, I can hear the fan continue to run as it shuts down to sleep/hibernate mode. And of course, when I plug it back in and press the power button, it takes a few moments to revive back to the original run state.

Another strange symptom, is that the system runs VERY slow. I've read elsewhere that a problem with a battery might cause a slower system.

I've tried the oft-recommended software PRAM and SMC reset through shut-down and using various key-presses. I've tried a hardware SMC reset by removing the battery and holding the power button for over 20 seconds. None of those worked. Of course, that also involved re-seating the battery. I've inspected the top of the logic board (without removing it) with a magnifier, no apparent discoloration or charring. No odd smell on the logic board either.

I've opened up a ticket with iFixit.com, but I figured I'd post here as well.