Olympic Stain problems Peeling . In Canada

Hello everyone, i am new to this forum  !

I live in New Brunswick Canada . Winters are harsh here .I had this deck built 5 years ago , i did nothing to it at first, the wood started turning grey and decided to do something about it before it got even worse, so i did some research and ended up with Olympic Maximum 6 year semi transparent stain.

I have a 40 x 45 deck with pressure treated wood , there is no shade anywhere on it.I use pressure treated wood, no mildew issues.The deck is well vented but there is a swimming pool  in the middle of it.The fence did not peel enough to make a fuss only the floor .

Before i did the job, i was told to wash it with their own brand wood prep , the next year the floor had peeled, so they warrantied it, but told me this time to sand the whole thing , which i did but this year, its the same thing again. At this point, i am not going to re do it with their stuff as i followed their instructions and , now i just think its junk.

I was told by backyard experts that its because its water base, i was also told  that here is Canada we cannot buy oil based stains anymore (If that's even the problem? or even the truth)

I hope i did not forget anything , i appreciate any and all help here. I do have pics of this time and last time that i can dig up if needed.