In the Pets tab There atre only 3 not 4 entries
The Entry for "Pet's you don't have at 24" is missing.

First I thought is is because of the new version 1.6 but I go back to 1.2 and the Entry is still missing.
Also deactivate every other addon to avoid interfering but no help

You'll need to change the settings to use replicate mode to see that button

This is these options:

Turn the replicate one on and then using the "Collecting(r)" tab in the auction house