It may be that this achievement is only active during Morostide, especially since it is listed under the seasonal Morostide achievements. I am however checking on this to make sure. As soon as I hear back I will let you know.

I checked and this should be working year round. Can you confirm that you are feeding your pet carved pumpkins? The uncarved ones do not count.

I am really sorry for the confusion! I know that is one that takes a bit of time. I hope you get it soon so you don't have to worry about it anymore!

Locking as resolved.