I have this question too, we have tried the various left cntrl + left option (alt) + left shift and power button for 5 seconds and the left command + left option + p + r + power and these do not work either, when you plug the power adapater in the green light comes on the adapter, but pressing the power button has no response.
Any help would be appreciated, had a trackpad replaced by apple genius 3-4 months ago, have booked another appointment for Saturday morning but could do without the 50 mile round trip for another fault.
Starting to wish we had bought a mac or ipad.
It's likely a hardware issue. At the very least it's beyond the usual SMC and PRAM rest techniques usually used to remedy certain power button issues. Looks like your Saturday appointment will be necessary.
The OP should try the SMC reset.