Sorry to hear. Check this thread in the bug report forums
https://us.forums.blizzard.com/en/wow/t/pet-battlecollection-broken/681040
Some of us are having this problem and the issue often relates to quest progress being reset.
For many it’s battle pet quest progress as well as other quests like islands, warfronts, some HoA quests, etc.
No acknowledgement as a known bug yet. Blizzard have stated in this forum in other threads that they would “forward on to the team”.
Most of us are just waiting to see what happens.