SMC reset problems/ battery is not recognized

[Mutopiano]

Got it. That makes a lot of sense. After all, it has been over two years since the laptop has been started. Replacement battery it is!

I was able to install a newer version of MacOS thanks to that little trick though. Thank you for your help, and I will follow up after the new battery installation.

 

[Mutopiano]

I think the issue may just be that the battery is so dead that recognizing ("perceiving" is pretty close, I think) the battery could be on the edge, so you lose it.
So, to modify what I suggested - if the battery is recognized as existing, and something registers in your System Information, then simply leave the MBPro charging for a few hours. I would let it go undisturbed for 24 hours, just to see if ANYTHING changes. ANY charge, ANY change to the data in System Information/Power tab.

However, I suspect that if you get ALL the battery test lights, and those lights shine without flashing or "racing" from one end of the lights to the other, then that should indicate that the system thinks your battery is fully charged, even though it is not close to that condition. At that point, you should try a different battery, either a new replacement, or one that you know is good. (and I think your existing battery has failed. I might be wrong (?) )

Alrighty. So I left the MagSafe plugged in overnight and the battery shows some information within the System Information tab. See attached images. However, this again is only possible if I disconnect and reconnect the battery to the logic board while the laptop is on. Could this mean a faulty/shorted connection cable running from the battery to the logic board? The piece of unplugging and plugging has me confused. It may be worth noting that after the unplug/plug process, the light on the MagSafe turned orange, even though the battery status said "Not Charging". Upon unplugging the MagSafe, the laptop died fairly quickly.

 

[DeltaMac]

Keep in mind that the magsafe LED has 3 colors. Green (power, no charging), Amber/orange (charging), and Red (a hardware error of some kind, often a fault in the battery) The red LED is not often seen, and ONLY appears when there is an actual hardware problem. You may be seeing orange, when the LED is actually red.
I would expect that you need to try a known-good battery - which you haven't tried yet, correct?

 

[Mutopiano]

That's correct. I have not tried yet. It looks to be amber/orange.

Any thoughts on the disconnecting/connecting piece? I find it odd that the MBP only detects the battery and MagSafe AFTER doing so.

 

[DeltaMac]

What you have is several possibilities, and you have to try one at a time, deciding as you go if the next step is worth the cost (and the effort)
There's not an easy way to prove what fixes it without trying each part.
Different DC-in board (the magsafe connector) - done, no help
New (or known-good) battery - your next step.
Logic board (which has the power and charging circuits) - this is where you need to decide to go ahead (or stop because,well, money)

 

[Mutopiano]

Looks like the new battery did the trick! Upon replacing with the new battery, the MBPro immediately detected the battery and MagSafe. I also rebooted to make sure it would detect after boot, which it did.
Thank you for all of your help! If anything pops up I will make sure to shoot a line here.