Free Chlorine ZERO

[mizzouguy]

Okay, neighbor having trouble this year pool has been cloudy for 3 weeks since opening. Pool is cloudy, these were test results:
Stabilizer-40
FC-0
CC-around 4
PH 7.8
Alk 140

Added shock yesterday to try to get to 10ppm checked today and 0 on FC. Went to store and added 13 gallons of 6% chlorine. Checked free chlorine 2 hours later and it is still Zero. How is this possible? The CC is around 2 now.

47,000 gallon liner pool, sand filter.

Any ideas why I can't get the FC chlorine to register.....my pool is registering fine, so I know it's not the test kit. He did take pool water to the store yesterday and they also had zero on the free chlorine.

Is 2 hours long enough to wait?
Is someting really eating the chloring up that fast?
One last thing he did that the pool store mentioned was to Floc....I've never heard of it so I don't know exactly what that is even though he explained it to me. He did that several days ago and didn't help.

thanks for any help!