Black Screen on 13" Macbook Pro 2019/Catalina. Resetting NVRAM/PRAM, SMC does not work
It sounds like you were able to restart, however I have experienced a similar black screen, which is some kind of hardware bug on the Macbook Pro. The screen will go black, but the computer is still running. Sometimes the screen will come back on its own; sometimes I can Command-Tab through programs and quit (I can see that I'm switching via the Touch bar); and sometimes I must restart. Over time, I have discovered that Google Chrome is the culprit, but exactly what is happening remains a mystery.

My thought in your case is that perhaps the processes that are causing this issue are resuming through restart. But obviously you'd see the Apple in this case, and it sounds like you're not seeing anything at all.

So maybe your graphics card has failed.