I'm unable to *click* on my trackpad or use it to move around the cursor.
The keyboard also doesn't work and won't light up, but the power button does work.
Try using a USB mouse & keyboard. If they both work, then you have a hardware issue with your laptop that will need to be repaired.
Hey did you get your issue resolved? I had/probably still the same problem, with another that immediately proceeded it. I've been looking for other people with the same problem. My thread is over here: https://discussions.apple.com/thread/252950157?page=1
I resolved mine by entering recovery, detailed in that thread, near the middle. Near the bottom, you might want to also read the thread ending in 749, she suggested a different solution that worked for her.
Broken keyboard/trackpad
