816G (indian dual sim) no rom installed, only cwm-recovery
I found the solution here:
http://forum.xda-developers.com/desire-816/help/816g-indian-dual-sim-rom-installed-cwm-t3302234

Basically, the backcover needs to be removed and the battery needs to disconnected in order to prevent a bootloop when connected to the pc via usb cable.

Flash this rom (http://www.needrom.com/download/htc-desire-816g-dual-sim/) using the SP Flash Tool for mt6592 (for example this tutorial: http://bm-smartphone-reviews.blogspot.de/2014/05/mt6592-flashing-tutorial.html)

Good luck