This was supposed to be resolved and the old thread was locked, but it's still not working for me. I tried refreshing as the thread suggested. Now when I have all the items it shows a "buy item" link as if I have none of them.
[edit] I'm using Safari / Mac OS. Is this browser dependent?

Which achievement? And make sure if it is a food achievement, that the same pet has eaten all the items; if a book achievement, the pet has read all the items; wardrobe, then they all need to be in your wardrobe and resave your HA to make sure it updates.
Dexter by ❤
It was 'have the food beanbags in your collection'. Do I have to go to my beanbag collection instead?
I had the same bug with a food achv earlier (drink up me hearties) but it gave me the achv after refreshing (even though it also said I didn't have any of the items)
[edit] It just worked. I went again just now and it had checkmarks, although it hadn't given me the achv; then Instead of refreshing I navigated away from the page.
