Once you download Pop 4S official firmware attached to this post, you need to unpack with 7-Zip (Windows), or via Terminal (if you use Linux) before flashing. Command to unpack in Ubuntu is:
tar -xvzf Alcatel_Pop_4S_5095K_20160912_(www.leakite.com).tar.xz
Alcatel Pop 4S ROM – Download
After unpacking the firmware as explained above, click here to follow flashing instructions.