How far are you into the Nightfallen storyline, Hobbitpolitics
? The majority of Pet Battle WQs that spawn in Suramar are gated behind reputation/quest chains.
I don't know the exact requirements, but the WQs seem to be tied to the quest area. Once you've completed the quest chain for the area the Pet Battle WQ spawns in, you should start seeing them.
I've heard some mentioning that they saw the WQs pop up after hitting 8k into honored with Nightfallen. But again, I don't think it's tied purely to reputation, and you may need to have "unlocked" certain areas by completing the quest chains for that area.