I got the guaranteed skill change coupon from Gula on login and tried to swap for the one skill that horse needed, S:Sideways, to be a courser and it just used one of the regular coupons I had and failed, giving me the only other skill the horse didn't already have. 

I figured it might have used the regular coupon as default so I used a storage maid to dump my skill change coupons into Deve's care, then tried again with only the event guaranteed swap coupon in my pearl tab.

"There is no item"

Anyone been able to use it / have it work, or is it bugged out?  I trained this horse myself, it's lvl 29 with 18/20 possible skills.  The event coupon tooltip says only once per mount but I know this mount has never had one used on it before, only the regular coupons swapping out Fore Chop whenever it was learned.

Disregard, it seems to have worked when I tried it at the Calpheon stable at the other end of my autoloop path.  Not sure what happened but it was likely user error somehow.

It worked

When it has that coupon instead of having only one button when you select the horse skill instead of two buttons, you have to press the one on the right to use it and have the guaranteed skill, I have already used it and I don't remember what is written on the button but if you do everything as I explained you should be able to use it. (sorry for my English)

I used it on a level 30 horse if by chance you can't use the coupon get it to 30.

Ok can someone tell me what im Reading incorrectly?  cux it clearly says to change a skill to one of my choosing. so why when i try it says no item?   maybe i need to relog.

OK so I finally figured it out ....   when you have selected the skills that you are trading and the skill you want to get, hit the Skill Selection Button it is next to the Change Skill Button....  that one is the one that activates the Guaranteed Skill change Token...thingy. I kept using Y on Keypad cux there is no way to click on that one, so i switched to keyboard and Mouse, and then i kept clicking on the change skill and it still said No Item ... so no don't click Change Skill. When you click the skill selection button it should say; are you sure you want to use the guaranted skill change? and then you have to confirm it.

So nope you thinking of a totally different Token... Alphaeus.

Token to change skill guaranteed does work just the UI is a mess ... 

I stand corrected.  Totally glad you figured it out.  I was trying to help trouble shoot, because I made that mistake a while back misreading the ticket.

my problem is different

so its trying to give me back the same skill i wanna get rid of?