I had the same issue and I can tell you that you just need the cable cuz the button bracket is broken. I just replaced my cable and I have a working sleep/wake function :)
It's time to speak out for your right to repair
We have a chance to guarantee our right to repair electronic
equipment—like smartphones, computers, and even farm equipment. This is a once-in-a-generation
chance to protect local repair jobs—the corner mom-and-pop repair shops that
keep getting squeezed out by manufacturers.
Join the cause and tell your state representative to support Right to Repair. Tell them you believe repair should be fair, affordable, and accessible. Stand up for your right to repair!