You will have to get more specific about your cya levels. If you have 0, then your chlorine will get eaten by the sunlight. If you have 30, You will have to shock up to 15ppms and keep it there till your chlorine holds overnight. It sounds like you are fighting left over algae. If you are unable to hold chlorine in your pool with a cya of 30, then there is something that is using up the chlorine.

here is the "best guess chart"

Stabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
=> 0 ppm . . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . . 8 ppm . . . . . 15 ppm . . .. 25 ppm



Your alkalinity and calcium are too high. In a vinyl pool you don't really need calcium. High calcium along with high alkalinity can make a pool cloudy - You may want to drain down 1/3, and refill.