My Mcb Pro 16” 2019 decided not to turn on

Hi everyone,
I’m hoping someone has seen this before.
I have a 2019 16-inch Intel MacBook Pro (Core i9, T2 chip). It had been sitting in a cupboard for about a month. I’m fairly certain I stored it with a full battery.
Today I plugged it into the charger and powered it on. It booted and showed 1% battery, then within a few seconds the fans ramped to maximum speed, and the Mac suddenly shut off.
Since then it has been completely dead.
Here’s what I’ve tried so far:
Left it charging for over 5 hours using the charger.
Tried all four USB-C ports.
Performed the T2 SMC reset multiple times.
Held the power button for 10, 15, and even 30 seconds.
Tried booting into Recovery.
No Apple logo, no keyboard backlight, no Touch Bar, no startup chime, no fan spin, and Caps Lock doesn’t respond.
The only thing I notice is that the right speaker area gets very slightly warm while it’s plugged in.
I also have another Mac (M1 Pro), so I tried using Apple Configurator to put the 2019 Mac into DFU mode for a firmware revive.
However, Apple Configurator never detects the Mac at all. The device never appears, so I can’t even attempt a Revive.
My questions are:
Does this sound like a dead battery, a logic board issue, or possibly a T2 firmware failure?
If the Mac won’t even show up in Apple Configurator, does that generally indicate a hardware failure?
Is there anything else I can try before taking it to Apple or an independent repair shop?
I’d really appreciate any suggestions or similar experiences.