Battery not charging on MacBook Pro (mid-2012)

Question

Seems to be a common problem, but so far, I haven't found a solution. I have a mid-2012 MacBook Pro 15" running OSMojave 10.14.6. The battery I'm currently using has seen days, but all sysinfo and coconut battery both indicate that it is in "good" or "normal" condition at 81% health. Currently clocking in at 1498 cycles, but no problems until last week. Now the green magsafe light will not turn to orange; there is a lightning bolt battery symbol, but it says "not charging" and will not charge. The laptop runs while plugged in with or without the battery.

Things I have tried:
• Multiple outlets, and multiple different charging blocks/ cords
• Cleaned and scrubbed the magsafe port.
• Opened up in recovery mode and run disk first aid.
• Reset the PRAM and NVRAM
• Tried SMC reset (shift-ctrl-opt-pwr for 10s), although I have no indication it did anything.
• I have tried to boot up in 'd' diagnostic mode, but I just get an error as it's apparently not supported on my device :/
• I have unplugged and removed the battery, waited, and then carefully put it all back together. I tried "discharging" it, but nothing happened.

All that has happened after all that was that my device ran at 1/3 the speed.... I haven't yet is reinstalled the OS or tried wiping it and recovering from a backup. I'm a little nervous about taking it in to an apple store and having them futz around doing the exact things I've already done before bricking it or telling me to get a new battery/ logic board, etc. etc. or buy a new computer. Obviously the battery as ancient, but I'd rather not buy a new one if it's not going to work anyway.
There was one time while my laptop and I were lying on our sides scrolling through websites to research the problem, that the charging status suddenly changed to "charging" and orange, and said "10hrs", but the charge never actually increased and when I shut down the computer to leave it alone, it changed back to green :[ I have not been able to replicate this.
UPDATE: I replaced the battery, but the situation remains the same. One new thing is when the computer is off and unconnected, connecting it will automatically start a boot. Which is weird.
UPDATE2: after leaving it plugged in for 24hrs, I disconnected the laptop to let it drain and re-charge it. As soon as I disconnected it, the computer shutdown, and when I tried to boot it, it chimed but the screen remained black. I typed in my password as if normal and eventually the loading screen came on. My new battery (cycle 1) now reads 7% and is not charging.
UPDATE3 (solution): I took it in to two repair specialists, including the Apple Store. Both suggested it was a DC-in board or logic board issue. Apple was unable to connect the computer to their network for diagnostic at all and suggested it was an I/O board issue. I ended up replacing the DC-in board (replacements are only ~$10) to no effect. Finally, I wiped my SSD, reinstalled the OS and restored to a backup. Now it is working. You guess is as good as mine.

Here are the deets:

Model Information:
  Serial Number: D86223102JFDGDLBT
Manufacturer: SMP
  Device Name: bq20z451
  Pack Lot Code: 0
  PCB Lot Code: 0
  Firmware Version: 406
  Hardware Revision: 2
  Cell Revision: 158

  Charge Information:
  Charge Remaining (mAh): 105
  Fully Charged: No
  Charging: No
  Full Charge Capacity (mAh): 5581

  Health Information:
  Cycle Count: 1498
  Condition: Normal
  Battery Installed: Yes
  Amperage (mA): 0
  Voltage (mV): 10943

Hardware Configuration:
  UPS Installed: No

AC Charger Information:
  Connected: Yes
  ID: 0x0100
  Wattage (W): 85
  Revision: 0x0000
  Family: 0x0085
  Serial Number: 0x0017e43d
  Charging: No

Battery 2
Battery Information:
Model Information:
Serial Number: C0171041G1WFY5QEP
Manufacturer: SMP
Device Name: A1382
Pack Lot Code: 0
PCB Lot Code: 0
Firmware Version: 702
Hardware Revision: 1
Cell Revision: 3217

Charge Information:
Charge Remaining (mAh): 508
Fully Charged: No
Charging: No
Full Charge Capacity (mAh): 7300
Health Information:
Cycle Count: 1
Condition: Normal
Battery Installed: Yes
Amperage (mA): 0
Voltage (mV): 10936

Hardware Configuration:
UPS Installed: No

AC Charger Information:
Connected: Yes
ID: 0x0100
Wattage (W): 85
Revision: 0x0000
Family: 0x0085
Serial Number: 0x0017e43d
Charging: No

Answer 1

Your battery is dead and needs to be replaced.

Specifically, it appears it’s no longer holding a charge, likely due to a failed cell(s).

 Health Information:
    Cycle Count: 1498
    Condition: Normal
    Battery Installed: Yes
    Amperage (mA): 0           <- This is a critical issue
    Voltage (mV): 10943.       <- Voltage is too low

According to your diagnostics, the battery is reporting OmA and just over 10V. The 0mA is most concerning because it means the battery has no power whatsoever. The voltage is low, too. It should be 18V (if memory serves), but regardless with 0mA of current, that battery isn’t going to drive anything.

The fact that it’s not charging and it’s age (~1500 cycles is at least 5 years), the battery is due to be replaced. Given the overall age of the device (11 years), it’s a good bet it’s not the original battery to begin with.

Answer 2

The problem has been fixed, though maybe not solved. Although I absolutely needed a new battery, this was not the specific problem here. I replaced the DC-in board, and that did not immediately fix the problem either. Only after I wiped my SSD, reinstalled the OS, AND restored to time machine backup did the light automatically turn to orange and read as "charging". It may have been a strange combination of things, but I cannot rule out simply reinstalling the OS and restoring to a previous version, since I had not previously tried that (it was a 7-hour process). I performed SMC and PRAM resets at every step. It is my personal opinion that my computer saw me looking at new laptops, got scared, and realized it had to shape up quick. Thank you to everyone who commented!

tl;dnr replaced the battery, replaced the DC-in board, reinstalled OS and restored from a backup.