Download Siswoo C55 Longbow official stock firmware from the link here, and follow the provided flashing instructions to learn how to flash the stock rom.
If you notice that any of the links provided below is broken or doesn’t work, please post in comments section so we fix and update it ASAP.
Download Options
File Name: C55_20151023.rar
Size: 849 MB
Android Version: 5.1
Release Date: 23/10/15
Firmware Link – Download
File Name: C55_20160128.zip
Size: 940 MB
Android Version: 5.1
Release Date: 28/01/16
Firmware Link – Download
How to flash
After downloading the Flashtool firmware, follow the instructions here to flash.