There is no keyboard sequence to startup your MacBook Pro if the start button is not working. If the start switch itself is defective, you can start by disassembling the machine and shorting out two points.
I would suggest you try another MagSafe Charger Adapter to see if that works as yours may be defective. Also your battery could be gone. And you didn't tell us which year and model MacBook Pro you have?
1. if the OP got that exact response from an "authorized" service center, he needs to find another shop to deal with, as he was misled.. There is no "unblocking" to be done on a MBP.
2. It could well be that the battery is bad, or the AC adaptor is bad (and then quite likley could've killed the battery).. try somebody else's magsafe (85w for 15"/17" and 60w for 13").. If a different adaptor works, you need to replace yours.
3. There are several kbd sequences which could help.
SMC reset: SHIFT+Control+Option+powerbutton... press this 2xs....
if it won't boot, theere's a more severe issue.
Theres' also an SMC bypass mode, which I can't remember off the top of my head. it essentially tells the SMC to boot and assume the machine needs all fans at full speed.. this will allow it to run (if there's no other major issue), but the fans will all scream..
I **THINK** SMC bypass is to remove AC, hold the power button down WHILE PLUGGING IN, and then releasing and pressing power button again.. you might google for that......