MacBook Pro Keyboard Malfunction After Sequoia Update

I upgraded my 16” MacBook Pro from macOS Sonoma to Sequoia a week ago(today is Nov 3, 2024). Immediately after the update, I couldn't log in because my keyboard stopped responding. I took it to the Apple Store, where I was told the keyboard is bad—a hardware issue—and that I’d need to pay $698 for a replacement. I pointed out that even the on-screen keyboard didn’t register key presses from the trackpad, but they seemed unsure how to respond and suggested the trackpad might also be faulty. It was alarming how they insisted it was a hardware issue, claiming the update had no connection to the problem and that my "S" key was damaged. ( it's not!!!) In reality, my MacBook was in perfect condition and functioning flawlessly before the Sequoia update, with no sign of any hardware issues.

After returning home, I contacted AppleCare to arrange for a repair. While troubleshooting, I discovered that pressing Option + Command + R at startup restored keyboard functionality temporarily, which was a relief. All the keys functioned perfectly, and the MacBook began running smoothly. It worked fine for about 3 hours, but then began experiencing keybord glitches and prompted me to upgrade to Sequoia 15.1. Unfortunately, after the update, my MacBook stopped recognizing the keyboard altogether and wouldn’t enter recovery mode, leaving it unusable. Pressing Option + Command + R at startup temporarily restores keyboard functionality. However, the fix only lasts for a short period before the issue reappears.

Also, since updating my Mac to Sequoia, it has started restarting on its own after shutting down.

My MacBook Pro is 2019 16" 16 GB RAM, 1TB. Never had any issues. ( The 14" MacBook that appears below is actually the new one I recently purchased—Apple mistakenly selected the wrong device.)

BTW, I purchased a brand new MacBook Pro with the M3 Pro chip just a few days ago. However, there are no available updates to upgrade from macOS Sonoma to Sequoia. I've even tried manually searching for updates, but Sequoia doesn’t appear as an option.