Why didn't the helo not fire any flares off?
Most likely because they didn't have comprehensive automated self defense suits installed.
MANPADS are IR guided, meaning there is no active signals emissions, so the only way an aircraft can know it is even under attack is if it has a good 360 MAWS installed or if the pilot was lucky enough to see the missile coming.
With the very short time between launch and impact (6-7 seconds in the video I posted, it is harder to tell with this new one), the self defense suit really needs to also be automated, as if you factor in the few seconds it will take for MAWS to detect and register the launch, as well as needing a second or two for the flares to deploy and disperse (most modern MANPADS have laser proximity fuses as well as impact fuses, so if your flares are not far enough away from the aircraft when the missile arrives, even if the missile seeker is spoofed and locks onto the flares, the proximity fuse might still set it off and shoot you down), you don't have all that many seconds left for a human to manually launch flares.
The FN-6 also has a modern seeker which has been designed to resist flares, so it really is a very scary weapon to be facing even with the most modern of self defense suits, that is why it is such a big deal that these weapons are not out of state control.