Chocobo whistle doesn't work?

[Vilthurnial]

Yesterday I obtained my chocobo whistle from Hantileon in San d'Oria (I am currently raising an adult chocobo there). I paid 250g to Hantileon to register my chocobo to ride. Today I reached level 20 and went outside (both W.Ronfaure and La Theine) to try it out. When activated the whistle reaches 5% - 8% and then just stops, the bar vanishes, nothing happens. When I try this I am in a zone that is chocobo okay, I am not moving, and I do not have hate/aggro from monsters.

I have seen lots of threads from other people with the same problem on other forums, but they never offer a solution and the people eventually stop posting, so either they figure it out and don't come back to post or they give up.

Any ideas?

Edit: I submitted a help desk call and the GM helpfully suggested via a form letter that I look online or talk to other players about my issue.

Edit 2: I've also tried re-registering my chocobo and dying (just for things to try)... no luck.