Originally Posted by apptum
Try holding one of the volume buttons while pressing power. A friend of mine had the same problem and we found this workaround accidentally.
No idea why it worked.
Thx for the tip but allready did that ant dont work. I also allready open the back cover for better pressing. is there maybe something that i can do with my pc that can force start it ? i saw something in youtube for the galaxy s2 they was using a JIG and a another way was using a flash software. Is there something like that for the htc one. please im desprate