I am guestimating that your pool is about 33k gallons from the dimensions and assuming a 3 ft shallow end and a rectangular pool. 10 lbs of CYA should certainly get you to about 40 ppm. Try an experiment to make sure your testing reagents are good. Take a sample of pool water and put it in the CYA dispensing vial to the water line and add 1 particle of CYA to it. Add the CYA reagent to the reagent line and shake for about 2 minutes and then let it sit for 5. The sample should turn very cloudy and when you put it into the CYA view tube it should read very high. If it does not then you probably have bad CYA reagent or the CYA is not CYA!

Also, have you cleaned or backwashed your filter after adding the CYA? If you did then it is possible that you washed it out of the pool before it all had a chance to dissolve.