Didn't completely bond to flexible PVC

I used this to fix three small leaks on a flexible PVC pipe running between my pool pump and filter. While I even waited for this to cure overnight, the leak was not completely stopped and there is still residual water leaking from the pipe. While this worked better than flex-seal or flex-tape; it was not bonded to the PVC, as the product stated it should be. I even used multiple layers and rubbed in the compound to get a good seal, and it still didn't bond.

###

