MacBook won't power on

About a month ago, I was using my MacBook Pro. The fans kicked in loudly and the touch bar went completely dark. Then the machine powered off. The middle of the back side was warmer than the rest of it. And then the machine wouldn't power on.

I plugged it in overnight and tried powering up again in the morning, but no luck. I tried resetting the NVRAM and SMC, but also no luck.

I bought a USB-C multimeter and tested each of the ports (there are 4). All but one started at 5V and ramped up to 20V, which is normal. One port consistently stayed at 5V. So I opened the MacBook and removed the port assembly. It was pretty dirty so I scraped off a lot of gunk. I then put the port back and tested it and it functioned normally (started at 5V and ramped up to 20V). So I charged the laptop overnight and tried it again. No luck. Nothing. I reset the NVRAM and SMC again. No change.

Using a regular multimeter I tested the battery. It barely registered, even when plugged in (0.024 volts).

What does this sound like to everyone? Bad battery? Or something else?