How can i get my phone working again (bootloader problem after unsucessfull root)

[AC Question]

I tried to root my htc one m9 . Somehow it failed and now its completly fcked . I cant reboot or do anything . I stuck on a black screen with a sliver htc logo and a red text:
Security Warning
If you flash this phone with any Rom
that was not officially released by HTC
you take the risk of
releasing your personal and financial information to unknown sources.

My HTC is S-On and relocked .
Nothing works . neither power or power + volume down .
pls help me i think my htc is completly broken.

 

[B. Diddy]

Moved to the M9 forum.

 

[xtralarge8]

I have the same problem right now. New phone, tried to upgrade to nougat, but somehow i managed to screw up. How did you solve the problem? Thanks.