The fact that *none* of your keys (the letter keys, other than shift, command, etc.) work makes it unlikely that it's one of those "single key stuck because of the bad design of the Mac butterfly keyboard" issues.
I'm thinking it may be configuration based, and a reset of the NVRAM and PRAM could do the trick. One of the settings that MacOS uses, and stores in those "non-volatile" areas of memory during shutdown, could potentially be causing the issue. It's a go-to step, beyond a full power-down and power-up (you've done that by pushing and holding down the power key, right?)
Instructions from Apple themselves are at
https://support.apple.com/en-us/HT204063
(and yes, the instructions involve holding down keys upon boot, when you are telling us that the keyboard does not work. I get that, but if it's config, option-command-P-R should work upon boot-up)