So, I'm at the point in the game after coming back from Terra but before going to finish the game/face Kuja at the Lifa Tree(so disc 4). I'm trying to finish up all my sidequests.

I have all the chocograph pieces and treasures, and I've dug up all the cracks and bubbles(i've double and triple checked this! even the spot where shimmering island was) I've also fixed Mognet Central with the Superslick(but i do have one letter that i can't deliver anymore, as gargant roo is now blocked off).

But nothing happens when I speak with Fat Chocobo. I've played cards with him but his dialogue never changes. The version of FF9 I have is downloaded from the playstation store.

Is anyone else having this problem? Am I missing something?

Welcome!

I'm sorry for the late reply - but to answer your question, I'm afraid it's been years since I played through FFIX sadly and the guide I used for Chocobo Hot and Cold I lost a long time ago. All I can suggest is to maybe look on GameFAQs for a guide which might have a solution. I do remember though that in disc 4 a lot of quests that were available in disc 3 become unavailable permanently, but I thought Chocobo Hot and Cold was unaffected. But I can't remember any more I'm sorry. :(

I don't know if this helps, but here's some instructions regarding the whole quest.

Final Fantasy 9 / IX / FF9 - Chocographs (http://www.uffsite.net/ff9/chocographs.php)

I have not played in a long while. I plan to eventually play it again. I don't' know what your trying to accomplish but if you found all the treasures then all is left is to face the optional boss. I don't remember if the fat chocobo gives anything out except just talking.