I have three pets but the achievement didn't track my progress, it's still 0/20. Do I have to do something for it to register my number of pets?

Strange. How long have you had all three? And have you clicked on the achievement or visited the pet page recently?

For a long time aha! Definitely more than a month. I've visited both and no luck :(

I just looked at the achievement page, and it shows 0/20 for me too (I've been here for 10+ years and currently have 19 pets). Sounds like a bug to me :D

Ahh!! Was about to send in a ticket aha hopefully staff is aware.

Maybe you could open a thread in the Bugs forums? I bet other people have this problem as well, I e.g. never looked at that achievement and never would have caught this :D

Good idea! Thank you :)

I went and checked mine. However it does seem I got mine before this has happened so I can't say if its recent or so old and people weren't aware.