Stuck on HtC boot window stating "This build is for development only"

I recently got unlocked HTC one m9 from one friend and i thought its international version. When i boot it to bootloader mode it shows "Unlocked" and "S-Off". I installed TWRP recovery and tried to root phone to flash viper rom but now phone goes into bootloop with red text "This build is for development purposes only…".
I am not sure what is going wrong and how do i get my phone back working. I appreciate if someone guide to get my phone working and root phone for custom rom.
Thank you in advance.

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