Why won't my HTC one m8 turn on?

[AC Question]

December 2015 my HTC one m8 stopped charging. I suspected it was the charging port. I got a new phone in January, but am trying to fix this one so a friend can use it. I bought a new charging port and installed it, everything went smoothly and the phone is charging without a problem! Sadly the power button now won't work. I don't know if this is because it has been dead for 5 months or what. I have tried all of the button combinations I've seen: holding power button, holding power button and volume buttons(for the whole 2 minutes), plugged it into the computer and tried that over and over again and the same thing while plugged into the wall charger. When I plug it into the computer, the computer notices I plugged in the phone and brings up htc sync manager, but once it searches it doesn't find a device. Please help! And thank you in advance

 

[belodion]

Try cleaning the button with a cotton bud and alcohol. I used that method myself to fix the home button on an ageing iPhone.