it shows that there is a fail stack for tier 6 to 7 pets. I've attempted about 10 6 to 7 exchanges which all failed but the stack still is at 0%. is that normal?? thx much in adv.

I think it is written in the help section under pet page that T6 pets undergo petscenscion BEFORE being able to raise them to T7. So what likely happened to yours is that you failed petscenscion 10 times. If the pet successfully petscends, then that is the time the fail stack will start to accumulate every failed attempt on the petscended pet.